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 $110.26   13.405%   $125.0404   $125.04   $125.05   $125.00  
  Purchase #2 $31.83   10.827%   $35.2762   $35.28   $35.30   $35.30  
  Purchase #3 $194.66   10.206%   $214.527   $214.53   $214.55   $214.50  
  Purchase #4 $41.61   6.376%   $44.2631   $44.26   $44.25   $44.30  
  Purchase #5 $49.41   11.681%   $55.1816   $55.18   $55.20   $55.20  
  Purchase #6 $5.81   8.366%   $6.2961   $6.30   $6.30   $6.30  
  Purchase #7 $135.82   7.387%   $145.853   $145.85   $145.85   $145.90  
  7 purchase totals = $569.40       $626.4374   $626.44   $626.50   $626.50