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 $69.36   3.412%   $71.7266   $71.73   $71.75   $71.70  
  Purchase #2 $83.81   6.213%   $89.0171   $89.02   $89.00   $89.00  
  Purchase #3 $205.61   11.228%   $228.6959   $228.70   $228.70   $228.70  
  Purchase #4 $250.73   9.476%   $274.4892   $274.49   $274.50   $274.50  
  Purchase #5 $189.80   10.490%   $209.71   $209.71   $209.70   $209.70  
  Purchase #6 $229.35   3.653%   $237.7282   $237.73   $237.75   $237.70  
  Purchase #7 $147.76   4.600%   $154.557   $154.56   $154.55   $154.60  
  7 purchase totals = $1,176.42       $1,265.9240   $1,265.94   $1,265.95   $1,265.90