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 $191.26   7.615%   $205.8244   $205.82   $205.80   $205.80  
  Purchase #2 $103.63   4.406%   $108.1959   $108.20   $108.20   $108.20  
  Purchase #3 $205.97   5.749%   $217.8112   $217.81   $217.80   $217.80  
  Purchase #4 $7.85   6.540%   $8.3634   $8.36   $8.35   $8.40  
  Purchase #5 $46.64   8.206%   $50.4673   $50.47   $50.45   $50.50  
  Purchase #6 $154.73   9.432%   $169.3241   $169.32   $169.30   $169.30  
  Purchase #7 $182.95   5.511%   $193.0324   $193.03   $193.05   $193.00  
  7 purchase totals = $893.03       $953.0187   $953.01   $952.95   $953.00