Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $194.98   6.660%   $207.9657   $207.97   $207.95   $208.00  
  Purchase #2 $181.36   6.580%   $193.2935   $193.29   $193.30   $193.30  
  Purchase #3 $213.99   5.195%   $225.1068   $225.11   $225.10   $225.10  
  Purchase #4 $179.77   11.509%   $200.4597   $200.46   $200.45   $200.50  
  Purchase #5 $245.33   10.459%   $270.9891   $270.99   $271.00   $271.00  
  Purchase #6 $222.63   10.596%   $246.2199   $246.22   $246.20   $246.20  
  Purchase #7 $213.79   7.823%   $230.5148   $230.51   $230.50   $230.50  
  7 purchase totals = $1,451.85       $1,574.5495   $1,574.55   $1,574.50   $1,574.60