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 $68.56   4.868%   $71.8975   $71.90   $71.90   $71.90  
  Purchase #2 $160.95   3.688%   $166.8858   $166.89   $166.90   $166.90  
  Purchase #3 $198.32   8.323%   $214.8262   $214.83   $214.85   $214.80  
  Purchase #4 $182.32   6.634%   $194.4151   $194.42   $194.40   $194.40  
  Purchase #5 $161.76   13.104%   $182.957   $182.96   $182.95   $183.00  
  Purchase #6 $239.66   9.125%   $261.529   $261.53   $261.55   $261.50  
  Purchase #7 $64.58   12.784%   $72.8359   $72.84   $72.85   $72.80  
  7 purchase totals = $1,076.15       $1,165.3465   $1,165.37   $1,165.40   $1,165.30