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 $95.45   6.432%   $101.5893   $101.59   $101.60   $101.60  
  Purchase #2 $5.62   4.732%   $5.8859   $5.89   $5.90   $5.90  
  Purchase #3 $180.95   6.259%   $192.2757   $192.28   $192.30   $192.30  
  Purchase #4 $246.31   10.553%   $272.3031   $272.30   $272.30   $272.30  
  Purchase #5 $32.48   8.168%   $35.133   $35.13   $35.15   $35.10  
  Purchase #6 $46.64   13.571%   $52.9695   $52.97   $52.95   $53.00  
  Purchase #7 $50.80   6.475%   $54.0893   $54.09   $54.10   $54.10  
  7 purchase totals = $658.25       $714.2458   $714.25   $714.30   $714.30