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	$191.74	11.825%	$214.4133	$214.41	$214.40	$214.40
Purchase #2	$246.67	6.511%	$262.7307	$262.73	$262.75	$262.70
Purchase #3	$75.90	7.667%	$81.7193	$81.72	$81.70	$81.70
Purchase #4	$97.32	13.565%	$110.5215	$110.52	$110.50	$110.50
Purchase #5	$155.46	11.554%	$173.4218	$173.42	$173.40	$173.40
Purchase #6	$11.98	12.250%	$13.4476	$13.45	$13.45	$13.40
Purchase #7	$245.81	3.855%	$255.286	$255.29	$255.30	$255.30
7 purchase totals =	$1,024.88		$1,111.5402	$1,111.54	$1,111.50	$1,111.40