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 $96.36   5.511%   $101.6704   $101.67   $101.65   $101.70  
  Purchase #2 $6.49   5.608%   $6.854   $6.85   $6.85   $6.90  
  Purchase #3 $76.79   10.677%   $84.9889   $84.99   $85.00   $85.00  
  Purchase #4 $213.47   5.309%   $224.8031   $224.80   $224.80   $224.80  
  Purchase #5 $126.95   6.727%   $135.4899   $135.49   $135.50   $135.50  
  Purchase #6 $167.73   9.194%   $183.1511   $183.15   $183.15   $183.20  
  Purchase #7 $191.62   12.547%   $215.6626   $215.66   $215.65   $215.70  
  7 purchase totals = $879.41       $952.6200   $952.61   $952.60   $952.80