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 $176.38   4.660%   $184.5993   $184.60   $184.60   $184.60  
  Purchase #2 $125.34   12.675%   $141.2268   $141.23   $141.25   $141.20  
  Purchase #3 $229.43   4.808%   $240.461   $240.46   $240.45   $240.50  
  Purchase #4 $149.54   12.766%   $168.6303   $168.63   $168.65   $168.60  
  Purchase #5 $214.33   4.467%   $223.9041   $223.90   $223.90   $223.90  
  Purchase #6 $231.73   9.228%   $253.114   $253.11   $253.10   $253.10  
  Purchase #7 $208.86   11.529%   $232.9395   $232.94   $232.95   $232.90  
  7 purchase totals = $1,335.61       $1,444.8750   $1,444.87   $1,444.90   $1,444.80