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 $57.57   5.538%   $60.7582   $60.76   $60.75   $60.80  
  Purchase #2 $208.29   3.103%   $214.7532   $214.75   $214.75   $214.80  
  Purchase #3 $120.82   8.504%   $131.0945   $131.09   $131.10   $131.10  
  Purchase #4 $49.59   3.434%   $51.2929   $51.29   $51.30   $51.30  
  Purchase #5 $146.53   3.665%   $151.9003   $151.90   $151.90   $151.90  
  Purchase #6 $27.78   3.457%   $28.7404   $28.74   $28.75   $28.70  
  Purchase #7 $57.79   9.642%   $63.3621   $63.36   $63.35   $63.40  
  7 purchase totals = $668.37       $701.9016   $701.89   $701.90   $702.00