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 $216.81   7.584%   $233.2529   $233.25   $233.25   $233.30  
  Purchase #2 $217.38   6.381%   $231.251   $231.25   $231.25   $231.30  
  Purchase #3 $226.48   13.467%   $256.9801   $256.98   $257.00   $257.00  
  Purchase #4 $174.71   13.696%   $198.6383   $198.64   $198.65   $198.60  
  Purchase #5 $236.36   4.488%   $246.9678   $246.97   $246.95   $247.00  
  Purchase #6 $157.75   13.105%   $178.4231   $178.42   $178.40   $178.40  
  Purchase #7 $19.62   13.197%   $22.2093   $22.21   $22.20   $22.20  
  7 purchase totals = $1,249.11       $1,367.7225   $1,367.72   $1,367.70   $1,367.80