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 $88.46   9.306%   $96.6921   $96.69   $96.70   $96.70  
  Purchase #2 $168.97   10.856%   $187.3134   $187.31   $187.30   $187.30  
  Purchase #3 $74.62   13.189%   $84.4616   $84.46   $84.45   $84.50  
  Purchase #4 $202.73   9.316%   $221.6163   $221.62   $221.60   $221.60  
  Purchase #5 $159.68   11.317%   $177.751   $177.75   $177.75   $177.80  
  Purchase #6 $238.37   9.794%   $261.716   $261.72   $261.70   $261.70  
  Purchase #7 $70.96   5.375%   $74.7741   $74.77   $74.75   $74.80  
  7 purchase totals = $1,003.79       $1,104.3245   $1,104.32   $1,104.25   $1,104.40