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 $44.99   4.401%   $46.97   $46.97   $46.95   $47.00  
  Purchase #2 $196.38   6.138%   $208.4338   $208.43   $208.45   $208.40  
  Purchase #3 $59.29   9.359%   $64.839   $64.84   $64.85   $64.80  
  Purchase #4 $218.99   6.432%   $233.0754   $233.08   $233.10   $233.10  
  Purchase #5 $119.98   12.614%   $135.1143   $135.11   $135.10   $135.10  
  Purchase #6 $113.37   10.425%   $125.1888   $125.19   $125.20   $125.20  
  Purchase #7 $147.76   5.737%   $156.237   $156.24   $156.25   $156.20  
  7 purchase totals = $900.76       $969.8583   $969.86   $969.90   $969.80