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 $61.35   10.858%   $68.0114   $68.01   $68.00   $68.00  
  Purchase #2 $85.70   13.345%   $97.1367   $97.14   $97.15   $97.10  
  Purchase #3 $168.63   3.826%   $175.0818   $175.08   $175.10   $175.10  
  Purchase #4 $67.30   4.414%   $70.2706   $70.27   $70.25   $70.30  
  Purchase #5 $46.41   7.412%   $49.8499   $49.85   $49.85   $49.80  
  Purchase #6 $51.63   4.421%   $53.9126   $53.91   $53.90   $53.90  
  Purchase #7 $247.66   3.693%   $256.8061   $256.81   $256.80   $256.80  
  7 purchase totals = $728.68       $771.0691   $771.07   $771.05   $771.00