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 $61.93   11.733%   $69.1962   $69.20   $69.20   $69.20  
  Purchase #2 $179.36   11.159%   $199.3748   $199.37   $199.35   $199.40  
  Purchase #3 $101.58   3.104%   $104.733   $104.73   $104.75   $104.70  
  Purchase #4 $200.43   6.115%   $212.6863   $212.69   $212.70   $212.70  
  Purchase #5 $11.75   3.637%   $12.1773   $12.18   $12.20   $12.20  
  Purchase #6 $160.38   7.192%   $171.9145   $171.91   $171.90   $171.90  
  Purchase #7 $155.89   10.579%   $172.3816   $172.38   $172.40   $172.40  
  7 purchase totals = $871.32       $942.4637   $942.46   $942.50   $942.50