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 $24.54   5.784%   $25.9594   $25.96   $25.95   $26.00  
  Purchase #2 $92.36   4.703%   $96.7037   $96.70   $96.70   $96.70  
  Purchase #3 $50.44   8.608%   $54.7819   $54.78   $54.80   $54.80  
  Purchase #4 $131.64   8.169%   $142.3937   $142.39   $142.40   $142.40  
  Purchase #5 $199.36   6.247%   $211.814   $211.81   $211.80   $211.80  
  Purchase #6 $11.56   12.637%   $13.0208   $13.02   $13.00   $13.00  
  Purchase #7 $171.59   3.767%   $178.0538   $178.05   $178.05   $178.10  
  7 purchase totals = $681.49       $722.7273   $722.71   $722.70   $722.80