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 $58.61   6.106%   $62.1887   $62.19   $62.20   $62.20  
  Purchase #2 $178.99   12.358%   $201.1096   $201.11   $201.10   $201.10  
  Purchase #3 $148.91   8.531%   $161.6135   $161.61   $161.60   $161.60  
  Purchase #4 $81.97   11.507%   $91.4023   $91.40   $91.40   $91.40  
  Purchase #5 $28.27   13.491%   $32.0839   $32.08   $32.10   $32.10  
  Purchase #6 $156.66   7.637%   $168.6241   $168.62   $168.60   $168.60  
  Purchase #7 $214.51   11.256%   $238.6552   $238.66   $238.65   $238.70  
  7 purchase totals = $867.92       $955.6773   $955.67   $955.65   $955.70