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 $61.33   4.209%   $63.9114   $63.91   $63.90   $63.90  
  Purchase #2 $24.95   12.666%   $28.1102   $28.11   $28.10   $28.10  
  Purchase #3 $90.92   5.861%   $96.2488   $96.25   $96.25   $96.20  
  Purchase #4 $57.76   13.211%   $65.3907   $65.39   $65.40   $65.40  
  Purchase #5 $216.92   8.813%   $236.0372   $236.04   $236.05   $236.00  
  Purchase #6 $216.48   7.172%   $232.0059   $232.01   $232.00   $232.00  
  Purchase #7 $24.45   5.219%   $25.726   $25.73   $25.75   $25.70  
  7 purchase totals = $692.81       $747.4302   $747.44   $747.45   $747.30