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 $96.47   5.260%   $101.5443   $101.54   $101.55   $101.50  
  Purchase #2 $92.95   6.721%   $99.1972   $99.20   $99.20   $99.20  
  Purchase #3 $70.72   7.495%   $76.0205   $76.02   $76.00   $76.00  
  Purchase #4 $65.47   6.252%   $69.5632   $69.56   $69.55   $69.60  
  Purchase #5 $22.97   9.546%   $25.1627   $25.16   $25.15   $25.20  
  Purchase #6 $41.42   6.493%   $44.1094   $44.11   $44.10   $44.10  
  Purchase #7 $191.49   5.692%   $202.3896   $202.39   $202.40   $202.40  
  7 purchase totals = $581.49       $617.9869   $617.98   $617.95   $618.00