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 $35.38   5.687%   $37.3921   $37.39   $37.40   $37.40  
  Purchase #2 $132.41   4.359%   $138.1818   $138.18   $138.20   $138.20  
  Purchase #3 $59.34   6.364%   $63.1164   $63.12   $63.10   $63.10  
  Purchase #4 $170.28   7.345%   $182.7871   $182.79   $182.80   $182.80  
  Purchase #5 $214.94   10.481%   $237.4679   $237.47   $237.45   $237.50  
  Purchase #6 $186.43   13.703%   $211.9765   $211.98   $212.00   $212.00  
  Purchase #7 $96.45   5.314%   $101.5754   $101.58   $101.60   $101.60  
  7 purchase totals = $895.23       $972.4972   $972.51   $972.55   $972.60