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 $59.61   3.713%   $61.8233   $61.82   $61.80   $61.80  
  Purchase #2 $168.88   11.665%   $188.5799   $188.58   $188.60   $188.60  
  Purchase #3 $241.39   10.215%   $266.048   $266.05   $266.05   $266.00  
  Purchase #4 $155.25   9.244%   $169.6013   $169.60   $169.60   $169.60  
  Purchase #5 $206.47   10.819%   $228.808   $228.81   $228.80   $228.80  
  Purchase #6 $70.81   8.773%   $77.0222   $77.02   $77.00   $77.00  
  Purchase #7 $212.37   5.751%   $224.5834   $224.58   $224.60   $224.60  
  7 purchase totals = $1,114.78       $1,216.4661   $1,216.46   $1,216.45   $1,216.40