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	$79.95	11.602%	$89.2258	$89.23	$89.25	$89.20
Purchase #2	$139.28	13.789%	$158.4853	$158.49	$158.50	$158.50
Purchase #3	$125.62	6.464%	$133.7401	$133.74	$133.75	$133.70
Purchase #4	$49.94	7.354%	$53.6126	$53.61	$53.60	$53.60
Purchase #5	$181.51	9.592%	$198.9204	$198.92	$198.90	$198.90
Purchase #6	$222.39	3.698%	$230.614	$230.61	$230.60	$230.60
Purchase #7	$185.90	10.647%	$205.6928	$205.69	$205.70	$205.70
7 purchase totals =	$984.59		$1,070.2910	$1,070.29	$1,070.30	$1,070.20