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	$94.50	11.726%	$105.5811	$105.58	$105.60	$105.60
Purchase #2	$94.36	11.179%	$104.9085	$104.91	$104.90	$104.90
Purchase #3	$228.83	3.608%	$237.0862	$237.09	$237.10	$237.10
Purchase #4	$233.85	6.185%	$248.3136	$248.31	$248.30	$248.30
Purchase #5	$107.57	3.252%	$111.0682	$111.07	$111.05	$111.10
Purchase #6	$150.99	5.102%	$158.6935	$158.69	$158.70	$158.70
Purchase #7	$71.37	4.297%	$74.4368	$74.44	$74.45	$74.40
7 purchase totals =	$981.47		$1,040.0879	$1,040.09	$1,040.10	$1,040.10