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 $59.68   4.726%   $62.5005   $62.50   $62.50   $62.50  
  Purchase #2 $55.31   9.559%   $60.5971   $60.60   $60.60   $60.60  
  Purchase #3 $11.99   11.871%   $13.4133   $13.41   $13.40   $13.40  
  Purchase #4 $115.69   3.107%   $119.2845   $119.28   $119.30   $119.30  
  Purchase #5 $106.49   11.755%   $119.0079   $119.01   $119.00   $119.00  
  Purchase #6 $199.76   7.596%   $214.9338   $214.93   $214.95   $214.90  
  Purchase #7 $145.35   3.539%   $150.4939   $150.49   $150.50   $150.50  
  7 purchase totals = $694.27       $740.2310   $740.22   $740.25   $740.20