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 $118.64   6.725%   $126.6185   $126.62   $126.60   $126.60  
  Purchase #2 $197.72   3.851%   $205.3342   $205.33   $205.35   $205.30  
  Purchase #3 $172.90   12.752%   $194.9482   $194.95   $194.95   $194.90  
  Purchase #4 $181.97   6.163%   $193.1848   $193.18   $193.20   $193.20  
  Purchase #5 $176.31   8.825%   $191.8694   $191.87   $191.85   $191.90  
  Purchase #6 $10.27   3.512%   $10.6307   $10.63   $10.65   $10.60  
  Purchase #7 $27.25   7.589%   $29.318   $29.32   $29.30   $29.30  
  7 purchase totals = $885.06       $951.9038   $951.90   $951.90   $951.80