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 $184.92   5.274%   $194.6727   $194.67   $194.65   $194.70  
  Purchase #2 $193.62   12.191%   $217.2242   $217.22   $217.20   $217.20  
  Purchase #3 $71.60   6.617%   $76.3378   $76.34   $76.35   $76.30  
  Purchase #4 $237.76   3.334%   $245.6869   $245.69   $245.70   $245.70  
  Purchase #5 $41.96   7.683%   $45.1838   $45.18   $45.20   $45.20  
  Purchase #6 $17.29   4.342%   $18.0407   $18.04   $18.05   $18.00  
  Purchase #7 $207.89   8.109%   $224.7478   $224.75   $224.75   $224.70  
  7 purchase totals = $955.04       $1,021.8939   $1,021.89   $1,021.90   $1,021.80