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 $55.46   11.707%   $61.9527   $61.95   $61.95   $62.00  
  Purchase #2 $207.50   4.569%   $216.9807   $216.98   $217.00   $217.00  
  Purchase #3 $191.91   8.235%   $207.7138   $207.71   $207.70   $207.70  
  Purchase #4 $98.87   12.233%   $110.9648   $110.96   $110.95   $111.00  
  Purchase #5 $185.88   6.382%   $197.7429   $197.74   $197.75   $197.70  
  Purchase #6 $34.29   6.304%   $36.4516   $36.45   $36.45   $36.50  
  Purchase #7 $41.45   5.137%   $43.5793   $43.58   $43.60   $43.60  
  7 purchase totals = $815.36       $875.3858   $875.37   $875.40   $875.50