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	$95.64	5.146%	$100.5616	$100.56	$100.55	$100.60
Purchase #2	$136.32	12.214%	$152.9701	$152.97	$152.95	$153.00
Purchase #3	$163.77	5.236%	$172.345	$172.35	$172.35	$172.30
Purchase #4	$98.60	12.691%	$111.1133	$111.11	$111.10	$111.10
Purchase #5	$46.83	13.820%	$53.3019	$53.30	$53.30	$53.30
Purchase #6	$87.66	10.860%	$97.1799	$97.18	$97.20	$97.20
Purchase #7	$52.60	3.324%	$54.3484	$54.35	$54.35	$54.30
7 purchase totals =	$681.42		$741.8202	$741.82	$741.80	$741.80