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	$167.69	4.248%	$174.8135	$174.81	$174.80	$174.80
Purchase #2	$118.29	10.678%	$130.921	$130.92	$130.90	$130.90
Purchase #3	$193.61	11.346%	$215.577	$215.58	$215.60	$215.60
Purchase #4	$9.70	6.139%	$10.2955	$10.30	$10.30	$10.30
Purchase #5	$72.74	8.111%	$78.6399	$78.64	$78.65	$78.60
Purchase #6	$99.70	13.574%	$113.2333	$113.23	$113.25	$113.20
Purchase #7	$56.99	9.707%	$62.522	$62.52	$62.50	$62.50
7 purchase totals =	$718.72		$786.0022	$786.00	$786.00	$785.90