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	$179.81	4.487%	$187.8781	$187.88	$187.90	$187.90
Purchase #2	$232.84	11.341%	$259.2464	$259.25	$259.25	$259.20
Purchase #3	$61.56	5.424%	$64.899	$64.90	$64.90	$64.90
Purchase #4	$137.58	11.257%	$153.0674	$153.07	$153.05	$153.10
Purchase #5	$169.56	7.422%	$182.1447	$182.14	$182.15	$182.10
Purchase #6	$189.33	11.643%	$211.3737	$211.37	$211.35	$211.40
Purchase #7	$37.45	10.172%	$41.2594	$41.26	$41.25	$41.30
7 purchase totals =	$1,008.13		$1,099.8687	$1,099.87	$1,099.85	$1,099.90