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 $91.61   3.237%   $94.5754   $94.58   $94.60   $94.60  
  Purchase #2 $151.31   9.485%   $165.6618   $165.66   $165.65   $165.70  
  Purchase #3 $229.88   5.560%   $242.6613   $242.66   $242.65   $242.70  
  Purchase #4 $199.47   7.164%   $213.76   $213.76   $213.75   $213.80  
  Purchase #5 $227.99   12.180%   $255.7592   $255.76   $255.75   $255.80  
  Purchase #6 $83.37   13.300%   $94.4582   $94.46   $94.45   $94.50  
  Purchase #7 $84.97   4.334%   $88.6526   $88.65   $88.65   $88.70  
  7 purchase totals = $1,068.60       $1,155.5285   $1,155.53   $1,155.50   $1,155.80