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 $195.48   4.658%   $204.5855   $204.59   $204.60   $204.60  
  Purchase #2 $205.53   11.811%   $229.8051   $229.81   $229.80   $229.80  
  Purchase #3 $25.49   8.862%   $27.7489   $27.75   $27.75   $27.70  
  Purchase #4 $73.82   6.216%   $78.4087   $78.41   $78.40   $78.40  
  Purchase #5 $54.81   9.642%   $60.0948   $60.09   $60.10   $60.10  
  Purchase #6 $64.84   6.450%   $69.0222   $69.02   $69.00   $69.00  
  Purchase #7 $73.78   12.392%   $82.9228   $82.92   $82.90   $82.90  
  7 purchase totals = $693.75       $752.5880   $752.59   $752.55   $752.50