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 $86.63   9.625%   $94.9681   $94.97   $94.95   $95.00  
  Purchase #2 $22.86   13.780%   $26.0101   $26.01   $26.00   $26.00  
  Purchase #3 $36.30   13.808%   $41.3123   $41.31   $41.30   $41.30  
  Purchase #4 $166.55   6.198%   $176.8728   $176.87   $176.85   $176.90  
  Purchase #5 $75.78   6.627%   $80.8019   $80.80   $80.80   $80.80  
  Purchase #6 $76.80   10.202%   $84.6351   $84.64   $84.65   $84.60  
  Purchase #7 $157.85   5.572%   $166.6454   $166.65   $166.65   $166.60  
  7 purchase totals = $622.77       $671.2457   $671.25   $671.20   $671.20