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 $131.98   10.785%   $146.214   $146.21   $146.20   $146.20  
  Purchase #2 $217.64   8.477%   $236.0893   $236.09   $236.10   $236.10  
  Purchase #3 $244.57   12.760%   $275.7771   $275.78   $275.80   $275.80  
  Purchase #4 $193.66   10.833%   $214.6392   $214.64   $214.65   $214.60  
  Purchase #5 $226.93   7.533%   $244.0246   $244.02   $244.00   $244.00  
  Purchase #6 $42.53   6.182%   $45.1592   $45.16   $45.15   $45.20  
  Purchase #7 $93.94   10.718%   $104.0085   $104.01   $104.00   $104.00  
  7 purchase totals = $1,151.25       $1,265.9119   $1,265.91   $1,265.90   $1,265.90