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 $195.96   3.197%   $202.2248   $202.22   $202.20   $202.20  
  Purchase #2 $66.34   7.863%   $71.5563   $71.56   $71.55   $71.60  
  Purchase #3 $233.83   4.430%   $244.1887   $244.19   $244.20   $244.20  
  Purchase #4 $20.95   7.615%   $22.5453   $22.55   $22.55   $22.50  
  Purchase #5 $101.69   7.432%   $109.2476   $109.25   $109.25   $109.20  
  Purchase #6 $97.34   13.655%   $110.6318   $110.63   $110.65   $110.60  
  Purchase #7 $176.29   8.701%   $191.629   $191.63   $191.65   $191.60  
  7 purchase totals = $892.40       $952.0235   $952.03   $952.05   $951.90