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 $206.96   5.312%   $217.9537   $217.95   $217.95   $218.00  
  Purchase #2 $56.78   10.378%   $62.6726   $62.67   $62.65   $62.70  
  Purchase #3 $65.52   9.719%   $71.8879   $71.89   $71.90   $71.90  
  Purchase #4 $20.62   10.252%   $22.734   $22.73   $22.75   $22.70  
  Purchase #5 $167.96   6.718%   $179.2436   $179.24   $179.25   $179.20  
  Purchase #6 $34.98   12.577%   $39.3794   $39.38   $39.40   $39.40  
  Purchase #7 $154.76   8.687%   $168.204   $168.20   $168.20   $168.20  
  7 purchase totals = $707.58       $762.0752   $762.06   $762.10   $762.10