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 $208.95   3.516%   $216.2967   $216.30   $216.30   $216.30  
  Purchase #2 $61.26   6.513%   $65.2499   $65.25   $65.25   $65.20  
  Purchase #3 $120.79   12.173%   $135.4938   $135.49   $135.50   $135.50  
  Purchase #4 $136.89   4.139%   $142.5559   $142.56   $142.55   $142.60  
  Purchase #5 $212.96   11.174%   $236.7562   $236.76   $236.75   $236.80  
  Purchase #6 $202.54   11.164%   $225.1516   $225.15   $225.15   $225.20  
  Purchase #7 $19.76   13.136%   $22.3557   $22.36   $22.35   $22.40  
  7 purchase totals = $963.15       $1,043.8598   $1,043.87   $1,043.85   $1,044.00