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 $246.26   7.490%   $264.7049   $264.70   $264.70   $264.70  
  Purchase #2 $55.69   9.482%   $60.9705   $60.97   $60.95   $61.00  
  Purchase #3 $190.68   8.773%   $207.4084   $207.41   $207.40   $207.40  
  Purchase #4 $70.80   9.312%   $77.3929   $77.39   $77.40   $77.40  
  Purchase #5 $192.61   9.177%   $210.2858   $210.29   $210.30   $210.30  
  Purchase #6 $195.57   10.509%   $216.1225   $216.12   $216.10   $216.10  
  Purchase #7 $89.26   10.182%   $98.3485   $98.35   $98.35   $98.30  
  7 purchase totals = $1,040.87       $1,135.2335   $1,135.23   $1,135.20   $1,135.20