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 $114.49   10.847%   $126.9087   $126.91   $126.90   $126.90  
  Purchase #2 $213.91   6.143%   $227.0505   $227.05   $227.05   $227.10  
  Purchase #3 $93.52   4.775%   $97.9856   $97.99   $98.00   $98.00  
  Purchase #4 $166.29   4.419%   $173.6384   $173.64   $173.65   $173.60  
  Purchase #5 $109.73   11.206%   $122.0263   $122.03   $122.05   $122.00  
  Purchase #6 $197.40   12.140%   $221.3644   $221.36   $221.35   $221.40  
  Purchase #7 $178.88   8.290%   $193.7092   $193.71   $193.70   $193.70  
  7 purchase totals = $1,074.22       $1,162.6831   $1,162.69   $1,162.70   $1,162.70