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 $28.69   11.629%   $32.0264   $32.03   $32.05   $32.00  
  Purchase #2 $234.99   3.202%   $242.5144   $242.51   $242.50   $242.50  
  Purchase #3 $107.34   11.591%   $119.7818   $119.78   $119.80   $119.80  
  Purchase #4 $77.83   13.562%   $88.3853   $88.39   $88.40   $88.40  
  Purchase #5 $191.29   3.299%   $197.6007   $197.60   $197.60   $197.60  
  Purchase #6 $141.40   5.451%   $149.1077   $149.11   $149.10   $149.10  
  Purchase #7 $226.76   11.815%   $253.5517   $253.55   $253.55   $253.60  
  7 purchase totals = $1,008.30       $1,082.9680   $1,082.97   $1,083.00   $1,083.00