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	$204.82	3.213%	$211.4009	$211.40	$211.40	$211.40
Purchase #2	$55.58	10.718%	$61.5371	$61.54	$61.55	$61.50
Purchase #3	$228.34	12.411%	$256.6793	$256.68	$256.70	$256.70
Purchase #4	$118.27	11.348%	$131.6913	$131.69	$131.70	$131.70
Purchase #5	$169.69	3.832%	$176.1925	$176.19	$176.20	$176.20
Purchase #6	$34.42	9.106%	$37.5543	$37.55	$37.55	$37.60
Purchase #7	$199.86	12.323%	$224.4887	$224.49	$224.50	$224.50
7 purchase totals =	$1,010.98		$1,099.5441	$1,099.54	$1,099.60	$1,099.60