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 $85.29   11.857%   $95.4028   $95.40   $95.40   $95.40  
  Purchase #2 $111.81   5.139%   $117.5559   $117.56   $117.55   $117.60  
  Purchase #3 $237.68   7.335%   $255.1138   $255.11   $255.10   $255.10  
  Purchase #4 $246.50   5.634%   $260.3878   $260.39   $260.40   $260.40  
  Purchase #5 $181.93   11.815%   $203.425   $203.43   $203.45   $203.40  
  Purchase #6 $100.83   6.333%   $107.2156   $107.22   $107.20   $107.20  
  Purchase #7 $208.26   6.379%   $221.5449   $221.54   $221.55   $221.50  
  7 purchase totals = $1,172.30       $1,260.6458   $1,260.65   $1,260.65   $1,260.60