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 $54.73   12.826%   $61.7497   $61.75   $61.75   $61.70  
  Purchase #2 $40.67   11.251%   $45.2458   $45.25   $45.25   $45.20  
  Purchase #3 $42.50   5.584%   $44.8732   $44.87   $44.85   $44.90  
  Purchase #4 $183.66   4.757%   $192.3967   $192.40   $192.40   $192.40  
  Purchase #5 $164.46   12.407%   $184.8646   $184.86   $184.85   $184.90  
  Purchase #6 $128.43   11.292%   $142.9323   $142.93   $142.95   $142.90  
  Purchase #7 $55.42   8.515%   $60.139   $60.14   $60.15   $60.10  
  7 purchase totals = $669.87       $732.2013   $732.20   $732.20   $732.10