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 $119.61   4.781%   $125.3286   $125.33   $125.35   $125.30  
  Purchase #2 $57.40   6.203%   $60.9605   $60.96   $60.95   $61.00  
  Purchase #3 $76.33   12.143%   $85.5988   $85.60   $85.60   $85.60  
  Purchase #4 $86.93   12.747%   $98.011   $98.01   $98.00   $98.00  
  Purchase #5 $100.92   5.362%   $106.3313   $106.33   $106.35   $106.30  
  Purchase #6 $185.64   12.372%   $208.6074   $208.61   $208.60   $208.60  
  Purchase #7 $193.63   9.219%   $211.4807   $211.48   $211.50   $211.50  
  7 purchase totals = $820.46       $896.3183   $896.32   $896.35   $896.30