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 $119.37   5.464%   $125.8924   $125.89   $125.90   $125.90  
  Purchase #2 $34.28   3.289%   $35.4075   $35.41   $35.40   $35.40  
  Purchase #3 $68.44   8.168%   $74.0302   $74.03   $74.05   $74.00  
  Purchase #4 $192.99   10.606%   $213.4585   $213.46   $213.45   $213.50  
  Purchase #5 $42.52   6.254%   $45.1792   $45.18   $45.20   $45.20  
  Purchase #6 $240.39   9.383%   $262.9458   $262.95   $262.95   $262.90  
  Purchase #7 $98.42   6.713%   $105.0269   $105.03   $105.05   $105.00  
  7 purchase totals = $796.41       $861.9405   $861.95   $862.00   $861.90