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 $58.82   6.866%   $62.8586   $62.86   $62.85   $62.90  
  Purchase #2 $50.37   11.377%   $56.1006   $56.10   $56.10   $56.10  
  Purchase #3 $60.68   5.132%   $63.7941   $63.79   $63.80   $63.80  
  Purchase #4 $157.84   7.441%   $169.5849   $169.58   $169.60   $169.60  
  Purchase #5 $201.89   7.844%   $217.7263   $217.73   $217.75   $217.70  
  Purchase #6 $185.74   8.535%   $201.5929   $201.59   $201.60   $201.60  
  Purchase #7 $157.79   11.824%   $176.4471   $176.45   $176.45   $176.40  
  7 purchase totals = $873.13       $948.1045   $948.10   $948.15   $948.10