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 $206.94   3.514%   $214.2119   $214.21   $214.20   $214.20  
  Purchase #2 $44.57   4.851%   $46.7321   $46.73   $46.75   $46.70  
  Purchase #3 $71.25   4.248%   $74.2767   $74.28   $74.30   $74.30  
  Purchase #4 $147.33   12.714%   $166.0615   $166.06   $166.05   $166.10  
  Purchase #5 $53.62   13.682%   $60.9563   $60.96   $60.95   $61.00  
  Purchase #6 $80.54   8.243%   $87.1789   $87.18   $87.20   $87.20  
  Purchase #7 $96.39   7.302%   $103.4284   $103.43   $103.45   $103.40  
  7 purchase totals = $700.64       $752.8458   $752.85   $752.90   $752.90