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 $88.46   8.430%   $95.9172   $95.92   $95.90   $95.90  
  Purchase #2 $209.77   4.127%   $218.4272   $218.43   $218.45   $218.40  
  Purchase #3 $126.52   4.500%   $132.2134   $132.21   $132.20   $132.20  
  Purchase #4 $97.98   9.674%   $107.4586   $107.46   $107.45   $107.50  
  Purchase #5 $222.93   12.872%   $251.6255   $251.63   $251.65   $251.60  
  Purchase #6 $241.97   5.828%   $256.072   $256.07   $256.05   $256.10  
  Purchase #7 $207.55   6.834%   $221.734   $221.73   $221.75   $221.70  
  7 purchase totals = $1,195.18       $1,283.4479   $1,283.45   $1,283.45   $1,283.40