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 $86.97   9.277%   $95.0382   $95.04   $95.05   $95.00  
  Purchase #2 $43.26   8.231%   $46.8207   $46.82   $46.80   $46.80  
  Purchase #3 $187.48   7.423%   $201.3966   $201.40   $201.40   $201.40  
  Purchase #4 $240.56   9.122%   $262.5039   $262.50   $262.50   $262.50  
  Purchase #5 $41.91   10.392%   $46.2653   $46.27   $46.25   $46.30  
  Purchase #6 $210.77   6.714%   $224.9211   $224.92   $224.90   $224.90  
  Purchase #7 $68.64   9.421%   $75.1066   $75.11   $75.10   $75.10  
  7 purchase totals = $879.59       $952.0524   $952.06   $952.00   $952.00