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 $60.95   3.136%   $62.8614   $62.86   $62.85   $62.90  
  Purchase #2 $5.99   5.533%   $6.3214   $6.32   $6.30   $6.30  
  Purchase #3 $196.68   12.435%   $221.1372   $221.14   $221.15   $221.10  
  Purchase #4 $164.26   10.736%   $181.895   $181.90   $181.90   $181.90  
  Purchase #5 $14.39   6.600%   $15.3397   $15.34   $15.35   $15.30  
  Purchase #6 $176.50   10.607%   $195.2214   $195.22   $195.20   $195.20  
  Purchase #7 $189.82   10.371%   $209.5062   $209.51   $209.50   $209.50  
  7 purchase totals = $808.59       $892.2823   $892.29   $892.25   $892.20