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	$151.31	4.197%	$157.6605	$157.66	$157.65	$157.70
Purchase #2	$124.61	5.795%	$131.8311	$131.83	$131.85	$131.80
Purchase #3	$230.25	8.688%	$250.2541	$250.25	$250.25	$250.30
Purchase #4	$79.51	13.396%	$90.1612	$90.16	$90.15	$90.20
Purchase #5	$150.85	10.530%	$166.7345	$166.73	$166.75	$166.70
Purchase #6	$122.38	6.561%	$130.4094	$130.41	$130.40	$130.40
Purchase #7	$67.52	4.714%	$70.7029	$70.70	$70.70	$70.70
7 purchase totals =	$926.43		$997.7537	$997.74	$997.75	$997.80