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 $174.47   7.526%   $187.6006   $187.60   $187.60   $187.60  
  Purchase #2 $216.41   12.131%   $242.6627   $242.66   $242.65   $242.70  
  Purchase #3 $112.61   4.789%   $118.0029   $118.00   $118.00   $118.00  
  Purchase #4 $174.38   7.119%   $186.7941   $186.79   $186.80   $186.80  
  Purchase #5 $151.84   4.102%   $158.0685   $158.07   $158.05   $158.10  
  Purchase #6 $171.99   13.210%   $194.7099   $194.71   $194.70   $194.70  
  Purchase #7 $10.25   10.756%   $11.3525   $11.35   $11.35   $11.40  
  7 purchase totals = $1,011.95       $1,099.1912   $1,099.18   $1,099.15   $1,099.30