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 $90.74   5.767%   $95.973   $95.97   $95.95   $96.00  
  Purchase #2 $157.68   10.181%   $173.7334   $173.73   $173.75   $173.70  
  Purchase #3 $99.75   9.293%   $109.0198   $109.02   $109.00   $109.00  
  Purchase #4 $111.62   7.711%   $120.227   $120.23   $120.25   $120.20  
  Purchase #5 $120.32   6.330%   $127.9363   $127.94   $127.95   $127.90  
  Purchase #6 $167.31   9.753%   $183.6277   $183.63   $183.65   $183.60  
  Purchase #7 $177.42   4.536%   $185.4678   $185.47   $185.45   $185.50  
  7 purchase totals = $924.84       $995.9850   $995.99   $996.00   $995.90