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 $53.99   7.605%   $58.0959   $58.10   $58.10   $58.10  
  Purchase #2 $218.99   10.489%   $241.9599   $241.96   $241.95   $242.00  
  Purchase #3 $26.98   6.354%   $28.6943   $28.69   $28.70   $28.70  
  Purchase #4 $215.25   5.332%   $226.7271   $226.73   $226.75   $226.70  
  Purchase #5 $196.58   9.804%   $215.8527   $215.85   $215.85   $215.90  
  Purchase #6 $173.76   4.845%   $182.1787   $182.18   $182.20   $182.20  
  Purchase #7 $99.64   8.619%   $108.228   $108.23   $108.25   $108.20  
  7 purchase totals = $985.19       $1,061.7366   $1,061.74   $1,061.80   $1,061.80