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 $92.75   3.559%   $96.051   $96.05   $96.05   $96.10  
  Purchase #2 $50.43   13.283%   $57.1286   $57.13   $57.15   $57.10  
  Purchase #3 $240.89   7.247%   $258.3473   $258.35   $258.35   $258.30  
  Purchase #4 $218.71   11.697%   $244.2925   $244.29   $244.30   $244.30  
  Purchase #5 $60.39   9.594%   $66.1838   $66.18   $66.20   $66.20  
  Purchase #6 $26.99   13.509%   $30.6361   $30.64   $30.65   $30.60  
  Purchase #7 $181.78   5.699%   $192.1396   $192.14   $192.15   $192.10  
  7 purchase totals = $871.94       $944.7789   $944.78   $944.85   $944.70