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	$239.51	11.149%	$266.213	$266.21	$266.20	$266.20
Purchase #2	$118.76	7.544%	$127.7193	$127.72	$127.70	$127.70
Purchase #3	$177.73	6.464%	$189.2185	$189.22	$189.20	$189.20
Purchase #4	$61.51	7.482%	$66.1122	$66.11	$66.10	$66.10
Purchase #5	$51.98	8.340%	$56.3151	$56.32	$56.30	$56.30
Purchase #6	$205.69	6.433%	$218.922	$218.92	$218.90	$218.90
Purchase #7	$92.64	8.263%	$100.2948	$100.29	$100.30	$100.30
7 purchase totals =	$947.82		$1,024.7949	$1,024.79	$1,024.70	$1,024.70