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	$164.84	4.554%	$172.3468	$172.35	$172.35	$172.30
Purchase #2	$116.47	9.852%	$127.9446	$127.94	$127.95	$127.90
Purchase #3	$122.44	13.629%	$139.1273	$139.13	$139.15	$139.10
Purchase #4	$183.36	12.308%	$205.9279	$205.93	$205.95	$205.90
Purchase #5	$153.75	6.754%	$164.1343	$164.13	$164.15	$164.10
Purchase #6	$167.39	12.285%	$187.9539	$187.95	$187.95	$188.00
Purchase #7	$58.70	13.208%	$66.4531	$66.45	$66.45	$66.50
7 purchase totals =	$966.95		$1,063.8879	$1,063.88	$1,063.95	$1,063.80