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 $221.82   5.323%   $233.6275   $233.63   $233.65   $233.60  
  Purchase #2 $176.66   10.581%   $195.3524   $195.35   $195.35   $195.40  
  Purchase #3 $60.78   12.609%   $68.4438   $68.44   $68.45   $68.40  
  Purchase #4 $214.64   11.367%   $239.0381   $239.04   $239.05   $239.00  
  Purchase #5 $74.47   3.713%   $77.2351   $77.24   $77.25   $77.20  
  Purchase #6 $111.91   9.128%   $122.1251   $122.13   $122.15   $122.10  
  Purchase #7 $7.91   8.748%   $8.602   $8.60   $8.60   $8.60  
  7 purchase totals = $868.19       $944.4240   $944.43   $944.50   $944.30