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 $87.38   9.598%   $95.7667   $95.77   $95.75   $95.80  
  Purchase #2 $43.81   10.180%   $48.2699   $48.27   $48.25   $48.30  
  Purchase #3 $87.64   11.213%   $97.4671   $97.47   $97.45   $97.50  
  Purchase #4 $196.83   3.661%   $204.0359   $204.04   $204.05   $204.00  
  Purchase #5 $190.81   4.401%   $199.2075   $199.21   $199.20   $199.20  
  Purchase #6 $31.40   10.698%   $34.7592   $34.76   $34.75   $34.80  
  Purchase #7 $238.94   6.743%   $255.0517   $255.05   $255.05   $255.10  
  7 purchase totals = $876.81       $934.5580   $934.57   $934.50   $934.70