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	$184.29	7.773%	$198.6149	$198.61	$198.60	$198.60
Purchase #2	$250.28	4.572%	$261.7228	$261.72	$261.70	$261.70
Purchase #3	$214.57	4.171%	$223.5197	$223.52	$223.50	$223.50
Purchase #4	$15.79	11.477%	$17.6022	$17.60	$17.60	$17.60
Purchase #5	$71.91	4.600%	$75.2179	$75.22	$75.20	$75.20
Purchase #6	$62.82	13.158%	$71.0859	$71.09	$71.10	$71.10
Purchase #7	$159.66	8.301%	$172.9134	$172.91	$172.90	$172.90
7 purchase totals =	$959.32		$1,020.6768	$1,020.67	$1,020.60	$1,020.60