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	$111.55	13.196%	$126.2701	$126.27	$126.25	$126.30
Purchase #2	$120.41	3.713%	$124.8808	$124.88	$124.90	$124.90
Purchase #3	$127.83	12.673%	$144.0299	$144.03	$144.05	$144.00
Purchase #4	$132.27	5.199%	$139.1467	$139.15	$139.15	$139.10
Purchase #5	$142.98	12.341%	$160.6252	$160.63	$160.65	$160.60
Purchase #6	$152.29	6.658%	$162.4295	$162.43	$162.45	$162.40
Purchase #7	$217.75	4.169%	$226.828	$226.83	$226.85	$226.80
7 purchase totals =	$1,005.08		$1,084.2102	$1,084.22	$1,084.30	$1,084.10