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 $44.64   4.278%   $46.5497   $46.55   $46.55   $46.50  
  Purchase #2 $183.92   8.572%   $199.6856   $199.69   $199.70   $199.70  
  Purchase #3 $148.77   11.633%   $166.0764   $166.08   $166.10   $166.10  
  Purchase #4 $212.59   5.721%   $224.7523   $224.75   $224.75   $224.80  
  Purchase #5 $248.51   9.185%   $271.3356   $271.34   $271.35   $271.30  
  Purchase #6 $137.31   12.225%   $154.0961   $154.10   $154.10   $154.10  
  Purchase #7 $139.50   10.359%   $153.9508   $153.95   $153.95   $154.00  
  7 purchase totals = $1,115.24       $1,216.4465   $1,216.46   $1,216.50   $1,216.50