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 $43.71   7.569%   $47.0184   $47.02   $47.00   $47.00  
  Purchase #2 $184.93   11.355%   $205.9288   $205.93   $205.95   $205.90  
  Purchase #3 $118.83   10.554%   $131.3713   $131.37   $131.35   $131.40  
  Purchase #4 $92.53   5.154%   $97.299   $97.30   $97.30   $97.30  
  Purchase #5 $118.59   7.128%   $127.0431   $127.04   $127.05   $127.00  
  Purchase #6 $129.29   9.304%   $141.3191   $141.32   $141.30   $141.30  
  Purchase #7 $188.27   5.554%   $198.7265   $198.73   $198.75   $198.70  
  7 purchase totals = $876.15       $948.7062   $948.71   $948.70   $948.60