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 $37.83   8.434%   $41.0206   $41.02   $41.00   $41.00  
  Purchase #2 $230.77   9.190%   $251.9778   $251.98   $252.00   $252.00  
  Purchase #3 $55.45   6.304%   $58.9456   $58.95   $58.95   $58.90  
  Purchase #4 $242.62   4.622%   $253.8339   $253.83   $253.85   $253.80  
  Purchase #5 $125.57   12.765%   $141.599   $141.60   $141.60   $141.60  
  Purchase #6 $226.36   7.616%   $243.5996   $243.60   $243.60   $243.60  
  Purchase #7 $242.93   8.116%   $262.6462   $262.65   $262.65   $262.60  
  7 purchase totals = $1,161.53       $1,253.6227   $1,253.63   $1,253.65   $1,253.50