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 $62.52   9.632%   $68.5419   $68.54   $68.55   $68.50  
  Purchase #2 $100.25   8.276%   $108.5467   $108.55   $108.55   $108.50  
  Purchase #3 $155.66   4.646%   $162.892   $162.89   $162.90   $162.90  
  Purchase #4 $206.39   4.572%   $215.8262   $215.83   $215.85   $215.80  
  Purchase #5 $69.81   3.329%   $72.134   $72.13   $72.15   $72.10  
  Purchase #6 $204.85   4.467%   $214.0006   $214.00   $214.00   $214.00  
  Purchase #7 $79.45   9.162%   $86.7292   $86.73   $86.75   $86.70  
  7 purchase totals = $878.93       $928.6706   $928.67   $928.75   $928.50