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 $62.38   11.860%   $69.7783   $69.78   $69.80   $69.80  
  Purchase #2 $125.98   3.697%   $130.6375   $130.64   $130.65   $130.60  
  Purchase #3 $5.69   13.818%   $6.4762   $6.48   $6.50   $6.50  
  Purchase #4 $46.37   8.845%   $50.4714   $50.47   $50.45   $50.50  
  Purchase #5 $73.60   4.868%   $77.1828   $77.18   $77.20   $77.20  
  Purchase #6 $189.93   12.732%   $214.1119   $214.11   $214.10   $214.10  
  Purchase #7 $187.31   4.624%   $195.9712   $195.97   $195.95   $196.00  
  7 purchase totals = $691.26       $744.6293   $744.63   $744.65   $744.70