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 $94.30   7.141%   $101.034   $101.03   $101.05   $101.00  
  Purchase #2 $35.81   7.113%   $38.3572   $38.36   $38.35   $38.40  
  Purchase #3 $44.79   4.296%   $46.7142   $46.71   $46.70   $46.70  
  Purchase #4 $85.30   8.248%   $92.3355   $92.34   $92.35   $92.30  
  Purchase #5 $157.68   7.303%   $169.1954   $169.20   $169.20   $169.20  
  Purchase #6 $224.28   4.471%   $234.3076   $234.31   $234.30   $234.30  
  Purchase #7 $210.43   12.129%   $235.9531   $235.95   $235.95   $236.00  
  7 purchase totals = $852.59       $917.8970   $917.90   $917.90   $917.90