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 $50.64   4.145%   $52.739   $52.74   $52.75   $52.70  
  Purchase #2 $174.71   4.670%   $182.869   $182.87   $182.85   $182.90  
  Purchase #3 $156.64   11.434%   $174.5502   $174.55   $174.55   $174.60  
  Purchase #4 $153.35   3.179%   $158.225   $158.23   $158.25   $158.20  
  Purchase #5 $126.35   10.385%   $139.4714   $139.47   $139.45   $139.50  
  Purchase #6 $211.43   8.255%   $228.8835   $228.88   $228.90   $228.90  
  Purchase #7 $92.86   5.182%   $97.672   $97.67   $97.65   $97.70  
  7 purchase totals = $965.98       $1,034.4101   $1,034.41   $1,034.40   $1,034.50