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 $167.27   10.813%   $185.3569   $185.36   $185.35   $185.40  
  Purchase #2 $64.54   12.118%   $72.361   $72.36   $72.35   $72.40  
  Purchase #3 $37.53   9.399%   $41.0574   $41.06   $41.05   $41.10  
  Purchase #4 $249.90   7.227%   $267.9603   $267.96   $267.95   $268.00  
  Purchase #5 $62.65   7.266%   $67.2021   $67.20   $67.20   $67.20  
  Purchase #6 $47.81   6.739%   $51.0319   $51.03   $51.05   $51.00  
  Purchase #7 $247.51   5.842%   $261.9695   $261.97   $261.95   $262.00  
  7 purchase totals = $877.21       $946.9391   $946.94   $946.90   $947.10