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 $56.84   7.186%   $60.9245   $60.92   $60.90   $60.90  
  Purchase #2 $88.71   8.332%   $96.1013   $96.10   $96.10   $96.10  
  Purchase #3 $158.40   7.818%   $170.7837   $170.78   $170.80   $170.80  
  Purchase #4 $215.87   8.253%   $233.6858   $233.69   $233.70   $233.70  
  Purchase #5 $23.93   10.406%   $26.4202   $26.42   $26.40   $26.40  
  Purchase #6 $57.98   3.670%   $60.1079   $60.11   $60.10   $60.10  
  Purchase #7 $100.53   4.193%   $104.7452   $104.75   $104.75   $104.70  
  7 purchase totals = $702.26       $752.7686   $752.77   $752.75   $752.70