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 $69.58   6.384%   $74.022   $74.02   $74.00   $74.00  
  Purchase #2 $140.80   7.507%   $151.3699   $151.37   $151.35   $151.40  
  Purchase #3 $168.82   3.839%   $175.301   $175.30   $175.30   $175.30  
  Purchase #4 $179.65   10.386%   $198.3084   $198.31   $198.30   $198.30  
  Purchase #5 $11.64   13.444%   $13.2049   $13.20   $13.20   $13.20  
  Purchase #6 $183.31   9.811%   $201.2945   $201.29   $201.30   $201.30  
  Purchase #7 $238.65   6.713%   $254.6706   $254.67   $254.65   $254.70  
  7 purchase totals = $992.45       $1,068.1713   $1,068.16   $1,068.10   $1,068.20