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 $119.53   5.446%   $126.0396   $126.04   $126.05   $126.00  
  Purchase #2 $98.82   8.860%   $107.5755   $107.58   $107.60   $107.60  
  Purchase #3 $244.48   4.113%   $254.5355   $254.54   $254.55   $254.50  
  Purchase #4 $105.80   6.120%   $112.275   $112.28   $112.30   $112.30  
  Purchase #5 $211.80   3.866%   $219.9882   $219.99   $220.00   $220.00  
  Purchase #6 $53.56   10.256%   $59.0531   $59.05   $59.05   $59.10  
  Purchase #7 $44.68   6.154%   $47.4296   $47.43   $47.45   $47.40  
  7 purchase totals = $878.67       $926.8965   $926.91   $927.00   $926.90