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	$217.73	11.780%	$243.3786	$243.38	$243.40	$243.40
Purchase #2	$227.40	12.637%	$256.1365	$256.14	$256.15	$256.10
Purchase #3	$163.63	7.827%	$176.4373	$176.44	$176.45	$176.40
Purchase #4	$129.76	12.386%	$145.8321	$145.83	$145.85	$145.80
Purchase #5	$198.43	12.177%	$222.5928	$222.59	$222.60	$222.60
Purchase #6	$85.30	5.653%	$90.122	$90.12	$90.10	$90.10
Purchase #7	$97.51	11.433%	$108.6583	$108.66	$108.65	$108.70
7 purchase totals =	$1,119.76		$1,243.1576	$1,243.16	$1,243.20	$1,243.10