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 $92.54   3.631%   $95.9001   $95.90   $95.90   $95.90  
  Purchase #2 $250.26   11.316%   $278.5794   $278.58   $278.60   $278.60  
  Purchase #3 $54.84   12.365%   $61.621   $61.62   $61.60   $61.60  
  Purchase #4 $172.49   4.844%   $180.8454   $180.85   $180.85   $180.80  
  Purchase #5 $150.77   7.484%   $162.0536   $162.05   $162.05   $162.10  
  Purchase #6 $250.65   10.418%   $276.7627   $276.76   $276.75   $276.80  
  Purchase #7 $140.42   7.710%   $151.2464   $151.25   $151.25   $151.20  
  7 purchase totals = $1,111.97       $1,207.0086   $1,207.01   $1,207.00   $1,207.00