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 $59.47   7.476%   $63.916   $63.92   $63.90   $63.90  
  Purchase #2 $59.60   3.407%   $61.6306   $61.63   $61.65   $61.60  
  Purchase #3 $98.90   6.348%   $105.1782   $105.18   $105.20   $105.20  
  Purchase #4 $170.82   7.138%   $183.0131   $183.01   $183.00   $183.00  
  Purchase #5 $198.27   8.147%   $214.4231   $214.42   $214.40   $214.40  
  Purchase #6 $213.35   8.738%   $231.9925   $231.99   $232.00   $232.00  
  Purchase #7 $36.97   3.327%   $38.2   $38.20   $38.20   $38.20  
  7 purchase totals = $837.38       $898.3535   $898.35   $898.35   $898.30