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 $69.54   5.171%   $73.1359   $73.14   $73.15   $73.10  
  Purchase #2 $24.69   9.149%   $26.9489   $26.95   $26.95   $26.90  
  Purchase #3 $241.78   6.102%   $256.5334   $256.53   $256.55   $256.50  
  Purchase #4 $216.81   11.171%   $241.0298   $241.03   $241.05   $241.00  
  Purchase #5 $23.40   3.149%   $24.1369   $24.14   $24.15   $24.10  
  Purchase #6 $209.57   13.222%   $237.2793   $237.28   $237.30   $237.30  
  Purchase #7 $5.82   11.694%   $6.5006   $6.50   $6.50   $6.50  
  7 purchase totals = $791.61       $865.5648   $865.57   $865.65   $865.40