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 $211.69   13.848%   $241.0048   $241.00   $241.00   $241.00  
  Purchase #2 $239.72   11.651%   $267.6498   $267.65   $267.65   $267.60  
  Purchase #3 $164.53   8.411%   $178.3686   $178.37   $178.35   $178.40  
  Purchase #4 $107.80   4.490%   $112.6402   $112.64   $112.65   $112.60  
  Purchase #5 $145.26   4.226%   $151.3987   $151.40   $151.40   $151.40  
  Purchase #6 $170.59   12.619%   $192.1168   $192.12   $192.10   $192.10  
  Purchase #7 $31.32   10.128%   $34.4921   $34.49   $34.50   $34.50  
  7 purchase totals = $1,070.91       $1,177.6710   $1,177.67   $1,177.65   $1,177.60