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 $60.64   13.726%   $68.9634   $68.96   $68.95   $69.00  
  Purchase #2 $200.70   10.436%   $221.6451   $221.65   $221.65   $221.60  
  Purchase #3 $115.44   9.287%   $126.1609   $126.16   $126.15   $126.20  
  Purchase #4 $62.61   3.271%   $64.658   $64.66   $64.65   $64.70  
  Purchase #5 $38.31   7.754%   $41.2806   $41.28   $41.30   $41.30  
  Purchase #6 $56.26   10.314%   $62.0627   $62.06   $62.05   $62.10  
  Purchase #7 $140.46   4.815%   $147.2231   $147.22   $147.20   $147.20  
  7 purchase totals = $674.42       $731.9938   $731.99   $731.95   $732.10