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	$173.25	5.398%	$182.602	$182.60	$182.60	$182.60
Purchase #2	$114.42	3.789%	$118.7554	$118.76	$118.75	$118.80
Purchase #3	$68.93	8.697%	$74.9248	$74.92	$74.90	$74.90
Purchase #4	$100.52	11.270%	$111.8486	$111.85	$111.85	$111.80
Purchase #5	$247.35	10.697%	$273.809	$273.81	$273.80	$273.80
Purchase #6	$197.54	12.852%	$222.9278	$222.93	$222.95	$222.90
Purchase #7	$136.30	12.743%	$153.6687	$153.67	$153.65	$153.70
7 purchase totals =	$1,038.31		$1,138.5363	$1,138.54	$1,138.50	$1,138.50