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	$175.94	11.766%	$196.6411	$196.64	$196.65	$196.60
Purchase #2	$81.42	10.621%	$90.0676	$90.07	$90.05	$90.10
Purchase #3	$179.27	12.325%	$201.365	$201.37	$201.35	$201.40
Purchase #4	$161.74	6.739%	$172.6397	$172.64	$172.65	$172.60
Purchase #5	$109.33	13.560%	$124.1551	$124.16	$124.15	$124.20
Purchase #6	$181.42	9.776%	$199.1556	$199.16	$199.15	$199.20
Purchase #7	$126.79	10.559%	$140.1778	$140.18	$140.20	$140.20
7 purchase totals =	$1,015.91		$1,124.2019	$1,124.22	$1,124.20	$1,124.30