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 $54.69   13.288%   $61.9572   $61.96   $61.95   $62.00  
  Purchase #2 $93.45   3.583%   $96.7983   $96.80   $96.80   $96.80  
  Purchase #3 $212.60   11.585%   $237.2297   $237.23   $237.25   $237.20  
  Purchase #4 $75.72   11.306%   $84.2809   $84.28   $84.30   $84.30  
  Purchase #5 $119.26   4.719%   $124.8879   $124.89   $124.90   $124.90  
  Purchase #6 $99.38   12.784%   $112.0847   $112.08   $112.10   $112.10  
  Purchase #7 $250.37   10.805%   $277.4225   $277.42   $277.40   $277.40  
  7 purchase totals = $905.47       $994.6612   $994.66   $994.70   $994.70