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	$151.25	4.797%	$158.5055	$158.51	$158.50	$158.50
Purchase #2	$94.92	3.743%	$98.4729	$98.47	$98.45	$98.50
Purchase #3	$127.70	3.277%	$131.8847	$131.88	$131.90	$131.90
Purchase #4	$165.28	13.240%	$187.1631	$187.16	$187.15	$187.20
Purchase #5	$144.88	6.743%	$154.6493	$154.65	$154.65	$154.60
Purchase #6	$166.89	11.797%	$186.578	$186.58	$186.60	$186.60
Purchase #7	$218.75	7.186%	$234.4694	$234.47	$234.45	$234.50
7 purchase totals =	$1,069.67		$1,151.7229	$1,151.72	$1,151.70	$1,151.80