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	$215.27	10.201%	$237.2297	$237.23	$237.25	$237.20
Purchase #2	$65.28	3.426%	$67.5165	$67.52	$67.50	$67.50
Purchase #3	$233.56	3.323%	$241.3212	$241.32	$241.30	$241.30
Purchase #4	$85.25	5.206%	$89.6881	$89.69	$89.70	$89.70
Purchase #5	$173.51	13.217%	$196.4428	$196.44	$196.45	$196.40
Purchase #6	$94.29	13.304%	$106.8343	$106.83	$106.85	$106.80
Purchase #7	$236.78	6.290%	$251.6735	$251.67	$251.65	$251.70
7 purchase totals =	$1,103.94		$1,190.7061	$1,190.70	$1,190.70	$1,190.60