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 $87.33   9.433%   $95.5678   $95.57   $95.55   $95.60  
  Purchase #2 $74.85   13.142%   $84.6868   $84.69   $84.70   $84.70  
  Purchase #3 $209.93   3.680%   $217.6554   $217.66   $217.65   $217.70  
  Purchase #4 $239.92   3.393%   $248.0605   $248.06   $248.05   $248.10  
  Purchase #5 $14.87   4.544%   $15.5457   $15.55   $15.55   $15.50  
  Purchase #6 $153.50   4.860%   $160.9601   $160.96   $160.95   $161.00  
  Purchase #7 $155.82   4.305%   $162.5281   $162.53   $162.55   $162.50  
  7 purchase totals = $936.22       $985.0044   $985.02   $985.00   $985.10