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	$153.49	13.108%	$173.6095	$173.61	$173.60	$173.60
Purchase #2	$171.40	8.198%	$185.4514	$185.45	$185.45	$185.50
Purchase #3	$199.50	4.297%	$208.0725	$208.07	$208.05	$208.10
Purchase #4	$191.89	6.215%	$203.816	$203.82	$203.80	$203.80
Purchase #5	$74.62	11.634%	$83.3013	$83.30	$83.30	$83.30
Purchase #6	$84.25	12.243%	$94.5647	$94.56	$94.55	$94.60
Purchase #7	$101.90	3.467%	$105.4329	$105.43	$105.45	$105.40
7 purchase totals =	$977.05		$1,054.2483	$1,054.24	$1,054.20	$1,054.30