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 $84.78   12.638%   $95.4945   $95.49   $95.50   $95.50  
  Purchase #2 $91.44   8.579%   $99.2846   $99.28   $99.30   $99.30  
  Purchase #3 $250.88   9.594%   $274.9494   $274.95   $274.95   $274.90  
  Purchase #4 $223.79   9.383%   $244.7882   $244.79   $244.80   $244.80  
  Purchase #5 $29.34   13.522%   $33.3074   $33.31   $33.30   $33.30  
  Purchase #6 $176.46   9.703%   $193.5819   $193.58   $193.60   $193.60  
  Purchase #7 $165.53   3.439%   $171.2226   $171.22   $171.20   $171.20  
  7 purchase totals = $1,022.22       $1,112.6286   $1,112.62   $1,112.65   $1,112.60