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 $117.90   8.236%   $127.6102   $127.61   $127.60   $127.60  
  Purchase #2 $90.84   7.395%   $97.5576   $97.56   $97.55   $97.60  
  Purchase #3 $69.69   12.179%   $78.1775   $78.18   $78.20   $78.20  
  Purchase #4 $39.58   5.635%   $41.8103   $41.81   $41.80   $41.80  
  Purchase #5 $206.79   5.174%   $217.4893   $217.49   $217.50   $217.50  
  Purchase #6 $101.85   4.124%   $106.0503   $106.05   $106.05   $106.10  
  Purchase #7 $85.38   12.675%   $96.2019   $96.20   $96.20   $96.20  
  7 purchase totals = $712.03       $764.8971   $764.90   $764.90   $765.00