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 $163.97   12.366%   $184.2465   $184.25   $184.25   $184.20  
  Purchase #2 $59.85   5.115%   $62.9113   $62.91   $62.90   $62.90  
  Purchase #3 $95.94   6.688%   $102.3565   $102.36   $102.35   $102.40  
  Purchase #4 $207.59   4.747%   $217.4443   $217.44   $217.45   $217.40  
  Purchase #5 $235.63   13.435%   $267.2869   $267.29   $267.30   $267.30  
  Purchase #6 $110.66   10.617%   $122.4088   $122.41   $122.40   $122.40  
  Purchase #7 $168.33   3.302%   $173.8883   $173.89   $173.90   $173.90  
  7 purchase totals = $1,041.97       $1,130.5426   $1,130.55   $1,130.55   $1,130.50