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	$134.55	7.345%	$144.4327	$144.43	$144.45	$144.40
Purchase #2	$173.55	13.118%	$196.3163	$196.32	$196.30	$196.30
Purchase #3	$208.27	10.778%	$230.7173	$230.72	$230.70	$230.70
Purchase #4	$101.79	9.764%	$111.7288	$111.73	$111.75	$111.70
Purchase #5	$59.49	5.467%	$62.7423	$62.74	$62.75	$62.70
Purchase #6	$210.41	6.432%	$223.9436	$223.94	$223.95	$223.90
Purchase #7	$176.72	11.730%	$197.4493	$197.45	$197.45	$197.40
7 purchase totals =	$1,064.78		$1,167.3303	$1,167.33	$1,167.35	$1,167.10