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 $56.48   9.750%   $61.9868   $61.99   $62.00   $62.00  
  Purchase #2 $227.95   3.324%   $235.5271   $235.53   $235.55   $235.50  
  Purchase #3 $168.82   10.133%   $185.9265   $185.93   $185.95   $185.90  
  Purchase #4 $202.58   9.549%   $221.9244   $221.92   $221.90   $221.90  
  Purchase #5 $182.55   7.809%   $196.8053   $196.81   $196.80   $196.80  
  Purchase #6 $93.56   13.554%   $106.2411   $106.24   $106.25   $106.20  
  Purchase #7 $36.63   3.638%   $37.9626   $37.96   $37.95   $38.00  
  7 purchase totals = $968.57       $1,046.3738   $1,046.38   $1,046.40   $1,046.30