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 $24.75   5.174%   $26.0306   $26.03   $26.05   $26.00  
  Purchase #2 $87.32   11.526%   $97.3845   $97.38   $97.40   $97.40  
  Purchase #3 $51.87   12.834%   $58.527   $58.53   $58.55   $58.50  
  Purchase #4 $223.75   6.417%   $238.108   $238.11   $238.10   $238.10  
  Purchase #5 $160.40   6.391%   $170.6512   $170.65   $170.65   $170.70  
  Purchase #6 $151.86   9.105%   $165.6869   $165.69   $165.70   $165.70  
  Purchase #7 $12.85   8.866%   $13.9893   $13.99   $14.00   $14.00  
  7 purchase totals = $712.80       $770.3775   $770.38   $770.45   $770.40