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 $145.67   11.606%   $162.5765   $162.58   $162.60   $162.60  
  Purchase #2 $229.90   7.306%   $246.6965   $246.70   $246.70   $246.70  
  Purchase #3 $134.51   8.829%   $146.3859   $146.39   $146.40   $146.40  
  Purchase #4 $213.67   10.629%   $236.381   $236.38   $236.40   $236.40  
  Purchase #5 $141.99   7.172%   $152.1735   $152.17   $152.15   $152.20  
  Purchase #6 $117.32   7.119%   $125.672   $125.67   $125.65   $125.70  
  Purchase #7 $54.56   11.428%   $60.7951   $60.80   $60.80   $60.80  
  7 purchase totals = $1,037.62       $1,130.6805   $1,130.69   $1,130.70   $1,130.80