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 $153.37   6.829%   $163.8436   $163.84   $163.85   $163.80  
  Purchase #2 $14.27   3.306%   $14.7418   $14.74   $14.75   $14.70  
  Purchase #3 $58.86   5.288%   $61.9725   $61.97   $61.95   $62.00  
  Purchase #4 $141.36   7.497%   $151.9578   $151.96   $151.95   $152.00  
  Purchase #5 $206.72   3.856%   $214.6911   $214.69   $214.70   $214.70  
  Purchase #6 $12.27   9.303%   $13.4115   $13.41   $13.40   $13.40  
  Purchase #7 $125.88   13.748%   $143.186   $143.19   $143.20   $143.20  
  7 purchase totals = $712.73       $763.8043   $763.80   $763.80   $763.80