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 $245.67   7.160%   $263.26   $263.26   $263.25   $263.30  
  Purchase #2 $119.85   6.286%   $127.3838   $127.38   $127.40   $127.40  
  Purchase #3 $84.88   4.550%   $88.742   $88.74   $88.75   $88.70  
  Purchase #4 $225.67   4.331%   $235.4438   $235.44   $235.45   $235.40  
  Purchase #5 $191.86   12.800%   $216.4181   $216.42   $216.40   $216.40  
  Purchase #6 $10.43   4.545%   $10.904   $10.90   $10.90   $10.90  
  Purchase #7 $236.75   6.464%   $252.0535   $252.05   $252.05   $252.10  
  7 purchase totals = $1,115.11       $1,194.2052   $1,194.19   $1,194.20   $1,194.20