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 $244.84   8.602%   $265.9011   $265.90   $265.90   $265.90  
  Purchase #2 $40.31   10.626%   $44.5933   $44.59   $44.60   $44.60  
  Purchase #3 $206.42   4.781%   $216.2889   $216.29   $216.30   $216.30  
  Purchase #4 $37.83   7.326%   $40.6014   $40.60   $40.60   $40.60  
  Purchase #5 $241.63   10.759%   $267.627   $267.63   $267.65   $267.60  
  Purchase #6 $57.80   11.254%   $64.3048   $64.30   $64.30   $64.30  
  Purchase #7 $197.45   8.233%   $213.7061   $213.71   $213.70   $213.70  
  7 purchase totals = $1,026.28       $1,113.0226   $1,113.02   $1,113.05   $1,113.00