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 $45.71   8.540%   $49.6136   $49.61   $49.60   $49.60  
  Purchase #2 $66.47   10.870%   $73.6953   $73.70   $73.70   $73.70  
  Purchase #3 $66.95   12.842%   $75.5477   $75.55   $75.55   $75.50  
  Purchase #4 $52.63   7.634%   $56.6478   $56.65   $56.65   $56.60  
  Purchase #5 $196.37   5.358%   $206.8915   $206.89   $206.90   $206.90  
  Purchase #6 $175.54   6.863%   $187.5873   $187.59   $187.60   $187.60  
  Purchase #7 $121.62   3.850%   $126.3024   $126.30   $126.30   $126.30  
  7 purchase totals = $725.29       $776.2856   $776.29   $776.30   $776.20