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 $57.69   7.388%   $61.9521   $61.95   $61.95   $62.00  
  Purchase #2 $49.77   9.822%   $54.6584   $54.66   $54.65   $54.70  
  Purchase #3 $13.40   5.457%   $14.1312   $14.13   $14.15   $14.10  
  Purchase #4 $94.92   10.688%   $105.065   $105.07   $105.05   $105.10  
  Purchase #5 $93.28   8.701%   $101.3963   $101.40   $101.40   $101.40  
  Purchase #6 $34.55   5.750%   $36.5366   $36.54   $36.55   $36.50  
  Purchase #7 $55.88   12.309%   $62.7583   $62.76   $62.75   $62.80  
  7 purchase totals = $399.49       $436.4979   $436.51   $436.50   $436.60