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 $161.63   3.250%   $166.883   $166.88   $166.90   $166.90  
  Purchase #2 $56.46   6.477%   $60.1169   $60.12   $60.10   $60.10  
  Purchase #3 $57.44   8.286%   $62.1995   $62.20   $62.20   $62.20  
  Purchase #4 $238.66   11.377%   $265.8123   $265.81   $265.80   $265.80  
  Purchase #5 $179.47   8.198%   $194.183   $194.18   $194.20   $194.20  
  Purchase #6 $44.70   3.848%   $46.4201   $46.42   $46.40   $46.40  
  Purchase #7 $50.47   7.117%   $54.0619   $54.06   $54.05   $54.10  
  7 purchase totals = $788.83       $849.6767   $849.67   $849.65   $849.70