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 $95.72   8.601%   $103.9529   $103.95   $103.95   $104.00  
  Purchase #2 $186.47   10.467%   $205.9878   $205.99   $206.00   $206.00  
  Purchase #3 $176.91   6.753%   $188.8567   $188.86   $188.85   $188.90  
  Purchase #4 $71.40   11.499%   $79.6103   $79.61   $79.60   $79.60  
  Purchase #5 $76.77   12.110%   $86.0668   $86.07   $86.05   $86.10  
  Purchase #6 $9.84   5.727%   $10.4035   $10.40   $10.40   $10.40  
  Purchase #7 $86.89   12.518%   $97.7669   $97.77   $97.75   $97.80  
  7 purchase totals = $704.00       $772.6449   $772.65   $772.60   $772.80