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 $214.77   4.840%   $225.1649   $225.16   $225.15   $225.20  
  Purchase #2 $53.61   9.341%   $58.6177   $58.62   $58.60   $58.60  
  Purchase #3 $237.71   13.547%   $269.9126   $269.91   $269.90   $269.90  
  Purchase #4 $60.82   4.507%   $63.5612   $63.56   $63.55   $63.60  
  Purchase #5 $181.43   8.217%   $196.3381   $196.34   $196.35   $196.30  
  Purchase #6 $223.28   9.397%   $244.2616   $244.26   $244.25   $244.30  
  Purchase #7 $12.68   3.647%   $13.1424   $13.14   $13.15   $13.10  
  7 purchase totals = $984.30       $1,070.9985   $1,070.99   $1,070.95   $1,071.00