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 $195.38   10.674%   $216.2349   $216.23   $216.25   $216.20  
  Purchase #2 $155.72   11.305%   $173.3241   $173.32   $173.30   $173.30  
  Purchase #3 $229.42   8.822%   $249.6594   $249.66   $249.65   $249.70  
  Purchase #4 $107.90   13.324%   $122.2766   $122.28   $122.30   $122.30  
  Purchase #5 $178.35   6.251%   $189.4987   $189.50   $189.50   $189.50  
  Purchase #6 $243.55   8.458%   $264.1495   $264.15   $264.15   $264.10  
  Purchase #7 $229.79   7.172%   $246.2705   $246.27   $246.25   $246.30  
  7 purchase totals = $1,340.11       $1,461.4137   $1,461.41   $1,461.40   $1,461.40