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 $53.36   10.276%   $58.8433   $58.84   $58.85   $58.80  
  Purchase #2 $217.35   11.497%   $242.3387   $242.34   $242.35   $242.30  
  Purchase #3 $190.73   5.773%   $201.7408   $201.74   $201.75   $201.70  
  Purchase #4 $83.73   3.331%   $86.519   $86.52   $86.50   $86.50  
  Purchase #5 $94.93   12.533%   $106.8276   $106.83   $106.85   $106.80  
  Purchase #6 $218.61   5.401%   $230.4171   $230.42   $230.40   $230.40  
  Purchase #7 $25.60   11.266%   $28.4841   $28.48   $28.50   $28.50  
  7 purchase totals = $884.31       $955.1706   $955.17   $955.20   $955.00