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	$131.88	10.432%	$145.6377	$145.64	$145.65	$145.60
Purchase #2	$213.43	7.537%	$229.5162	$229.52	$229.50	$229.50
Purchase #3	$88.80	11.806%	$99.2837	$99.28	$99.30	$99.30
Purchase #4	$101.88	11.335%	$113.4281	$113.43	$113.45	$113.40
Purchase #5	$113.44	9.324%	$124.0171	$124.02	$124.00	$124.00
Purchase #6	$217.71	13.195%	$246.4368	$246.44	$246.45	$246.40
Purchase #7	$204.83	8.452%	$222.1422	$222.14	$222.15	$222.10
7 purchase totals =	$1,071.97		$1,180.4618	$1,180.47	$1,180.50	$1,180.30