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	$105.72	5.378%	$111.4056	$111.41	$111.40	$111.40
Purchase #2	$155.38	10.839%	$172.2216	$172.22	$172.20	$172.20
Purchase #3	$245.62	13.249%	$278.1622	$278.16	$278.15	$278.20
Purchase #4	$133.80	10.125%	$147.3473	$147.35	$147.35	$147.30
Purchase #5	$43.31	6.575%	$46.1576	$46.16	$46.15	$46.20
Purchase #6	$72.97	4.594%	$76.3222	$76.32	$76.30	$76.30
Purchase #7	$40.73	7.245%	$43.6809	$43.68	$43.70	$43.70
7 purchase totals =	$797.53		$875.2974	$875.30	$875.25	$875.30