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 $215.75   13.616%   $245.1265   $245.13   $245.15   $245.10  
  Purchase #2 $155.88   8.399%   $168.9724   $168.97   $168.95   $169.00  
  Purchase #3 $148.83   12.185%   $166.9649   $166.96   $166.95   $167.00  
  Purchase #4 $216.36   8.597%   $234.9605   $234.96   $234.95   $235.00  
  Purchase #5 $245.54   13.355%   $278.3319   $278.33   $278.35   $278.30  
  Purchase #6 $65.25   5.133%   $68.5993   $68.60   $68.60   $68.60  
  Purchase #7 $221.76   13.356%   $251.3783   $251.38   $251.40   $251.40  
  7 purchase totals = $1,269.37       $1,414.3338   $1,414.33   $1,414.35   $1,414.40