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	$53.32	10.749%	$59.0514	$59.05	$59.05	$59.10
Purchase #2	$235.62	4.407%	$246.0038	$246.00	$246.00	$246.00
Purchase #3	$179.30	3.407%	$185.4088	$185.41	$185.40	$185.40
Purchase #4	$41.75	3.431%	$43.1824	$43.18	$43.20	$43.20
Purchase #5	$158.91	4.681%	$166.3486	$166.35	$166.35	$166.30
Purchase #6	$19.43	13.237%	$22.0019	$22.00	$22.00	$22.00
Purchase #7	$9.61	12.643%	$10.825	$10.83	$10.85	$10.80
7 purchase totals =	$697.94		$732.8219	$732.82	$732.85	$732.80