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 $86.95   5.382%   $91.6296   $91.63   $91.65   $91.60  
  Purchase #2 $23.89   4.734%   $25.021   $25.02   $25.00   $25.00  
  Purchase #3 $60.93   8.225%   $65.9415   $65.94   $65.95   $65.90  
  Purchase #4 $7.59   5.481%   $8.006   $8.01   $8.00   $8.00  
  Purchase #5 $23.41   9.609%   $25.6595   $25.66   $25.65   $25.70  
  Purchase #6 $242.85   13.207%   $274.9232   $274.92   $274.90   $274.90  
  Purchase #7 $249.45   9.347%   $272.7661   $272.77   $272.75   $272.80  
  7 purchase totals = $695.07       $763.9469   $763.95   $763.90   $763.90