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 $169.64   7.513%   $182.3851   $182.39   $182.40   $182.40  
  Purchase #2 $136.77   3.104%   $141.0153   $141.02   $141.00   $141.00  
  Purchase #3 $81.60   3.609%   $84.5449   $84.54   $84.55   $84.50  
  Purchase #4 $68.62   6.327%   $72.9616   $72.96   $72.95   $73.00  
  Purchase #5 $250.94   4.261%   $261.6326   $261.63   $261.65   $261.60  
  Purchase #6 $162.56   8.253%   $175.9761   $175.98   $176.00   $176.00  
  Purchase #7 $200.97   3.558%   $208.1205   $208.12   $208.10   $208.10  
  7 purchase totals = $1,071.10       $1,126.6361   $1,126.64   $1,126.65   $1,126.60