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 $216.97   4.706%   $227.1806   $227.18   $227.20   $227.20  
  Purchase #2 $201.94   4.848%   $211.7301   $211.73   $211.75   $211.70  
  Purchase #3 $237.35   7.223%   $254.4938   $254.49   $254.50   $254.50  
  Purchase #4 $183.28   4.612%   $191.7329   $191.73   $191.75   $191.70  
  Purchase #5 $131.26   13.813%   $149.3909   $149.39   $149.40   $149.40  
  Purchase #6 $163.31   8.130%   $176.5871   $176.59   $176.60   $176.60  
  Purchase #7 $116.99   13.474%   $132.7532   $132.75   $132.75   $132.80  
  7 purchase totals = $1,251.10       $1,343.8686   $1,343.86   $1,343.95   $1,343.90