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 $87.95   9.546%   $96.3457   $96.35   $96.35   $96.30  
  Purchase #2 $209.93   13.833%   $238.9696   $238.97   $238.95   $239.00  
  Purchase #3 $48.48   12.211%   $54.3999   $54.40   $54.40   $54.40  
  Purchase #4 $141.97   7.420%   $152.5042   $152.50   $152.50   $152.50  
  Purchase #5 $130.77   4.473%   $136.6193   $136.62   $136.60   $136.60  
  Purchase #6 $54.37   4.430%   $56.7786   $56.78   $56.80   $56.80  
  Purchase #7 $202.97   6.525%   $216.2138   $216.21   $216.20   $216.20  
  7 purchase totals = $876.44       $951.8311   $951.83   $951.80   $951.80