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 $61.61   11.830%   $68.8985   $68.90   $68.90   $68.90  
  Purchase #2 $214.60   10.299%   $236.7017   $236.70   $236.70   $236.70  
  Purchase #3 $117.87   10.565%   $130.323   $130.32   $130.30   $130.30  
  Purchase #4 $95.37   4.498%   $99.6597   $99.66   $99.65   $99.70  
  Purchase #5 $169.96   7.650%   $182.9619   $182.96   $182.95   $183.00  
  Purchase #6 $149.30   4.433%   $155.9185   $155.92   $155.90   $155.90  
  Purchase #7 $9.97   13.643%   $11.3302   $11.33   $11.35   $11.30  
  7 purchase totals = $818.68       $885.7935   $885.79   $885.75   $885.80