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 $96.41   7.450%   $103.5925   $103.59   $103.60   $103.60  
  Purchase #2 $237.49   4.293%   $247.6854   $247.69   $247.70   $247.70  
  Purchase #3 $152.51   6.312%   $162.1364   $162.14   $162.15   $162.10  
  Purchase #4 $96.96   5.208%   $102.0097   $102.01   $102.00   $102.00  
  Purchase #5 $22.45   13.142%   $25.4004   $25.40   $25.40   $25.40  
  Purchase #6 $179.98   8.836%   $195.883   $195.88   $195.90   $195.90  
  Purchase #7 $108.83   9.125%   $118.7607   $118.76   $118.75   $118.80  
  7 purchase totals = $894.63       $955.4681   $955.47   $955.50   $955.50