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	$187.99	4.771%	$196.959	$196.96	$196.95	$197.00
Purchase #2	$186.37	5.426%	$196.4824	$196.48	$196.50	$196.50
Purchase #3	$155.63	11.658%	$173.7733	$173.77	$173.75	$173.80
Purchase #4	$192.25	6.700%	$205.1308	$205.13	$205.15	$205.10
Purchase #5	$142.99	10.457%	$157.9425	$157.94	$157.95	$157.90
Purchase #6	$173.78	3.491%	$179.8467	$179.85	$179.85	$179.80
Purchase #7	$124.82	4.750%	$130.749	$130.75	$130.75	$130.70
7 purchase totals =	$1,163.83		$1,240.8837	$1,240.88	$1,240.90	$1,240.80