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	$178.55	11.145%	$198.4494	$198.45	$198.45	$198.40
Purchase #2	$90.52	11.495%	$100.9253	$100.93	$100.95	$100.90
Purchase #3	$162.86	11.714%	$181.9374	$181.94	$181.95	$181.90
Purchase #4	$38.68	10.706%	$42.8211	$42.82	$42.80	$42.80
Purchase #5	$102.69	4.721%	$107.538	$107.54	$107.55	$107.50
Purchase #6	$112.32	13.227%	$127.1766	$127.18	$127.20	$127.20
Purchase #7	$97.77	8.213%	$105.7999	$105.80	$105.80	$105.80
7 purchase totals =	$783.39		$864.6477	$864.66	$864.70	$864.50