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 $32.66   11.359%   $36.3698   $36.37   $36.35   $36.40  
  Purchase #2 $190.74   10.360%   $210.5007   $210.50   $210.50   $210.50  
  Purchase #3 $53.29   10.250%   $58.7522   $58.75   $58.75   $58.80  
  Purchase #4 $247.79   13.718%   $281.7818   $281.78   $281.80   $281.80  
  Purchase #5 $90.81   7.780%   $97.875   $97.88   $97.90   $97.90  
  Purchase #6 $214.56   10.433%   $236.945   $236.95   $236.95   $236.90  
  Purchase #7 $43.38   5.277%   $45.6692   $45.67   $45.65   $45.70  
  7 purchase totals = $873.23       $967.8937   $967.90   $967.90   $968.00