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 $60.45   3.811%   $62.7537   $62.75   $62.75   $62.80  
  Purchase #2 $241.41   9.417%   $264.1436   $264.14   $264.15   $264.10  
  Purchase #3 $147.64   9.276%   $161.3351   $161.34   $161.35   $161.30  
  Purchase #4 $107.50   6.388%   $114.3671   $114.37   $114.35   $114.40  
  Purchase #5 $15.44   7.184%   $16.5492   $16.55   $16.55   $16.50  
  Purchase #6 $86.49   7.634%   $93.0926   $93.09   $93.10   $93.10  
  Purchase #7 $229.34   9.120%   $250.2558   $250.26   $250.25   $250.30  
  7 purchase totals = $888.27       $962.4971   $962.50   $962.50   $962.50