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 $69.56   10.714%   $77.0127   $77.01   $77.00   $77.00  
  Purchase #2 $118.78   6.864%   $126.9331   $126.93   $126.95   $126.90  
  Purchase #3 $13.61   10.834%   $15.0845   $15.08   $15.10   $15.10  
  Purchase #4 $244.65   12.367%   $274.9059   $274.91   $274.90   $274.90  
  Purchase #5 $44.96   6.756%   $47.9975   $48.00   $48.00   $48.00  
  Purchase #6 $58.72   8.457%   $63.686   $63.69   $63.70   $63.70  
  Purchase #7 $119.36   5.450%   $125.8651   $125.87   $125.85   $125.90  
  7 purchase totals = $669.64       $731.4848   $731.49   $731.50   $731.50