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 $70.96   8.449%   $76.9554   $76.96   $76.95   $77.00  
  Purchase #2 $146.71   4.251%   $152.9466   $152.95   $152.95   $152.90  
  Purchase #3 $124.80   11.826%   $139.5588   $139.56   $139.55   $139.60  
  Purchase #4 $69.47   12.757%   $78.3323   $78.33   $78.35   $78.30  
  Purchase #5 $237.73   9.354%   $259.9673   $259.97   $259.95   $260.00  
  Purchase #6 $218.63   11.153%   $243.0138   $243.01   $243.00   $243.00  
  Purchase #7 $218.63   8.661%   $237.5655   $237.57   $237.55   $237.60  
  7 purchase totals = $1,086.93       $1,188.3397   $1,188.35   $1,188.30   $1,188.40