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	$214.56	13.390%	$243.2896	$243.29	$243.30	$243.30
Purchase #2	$26.61	5.176%	$27.9873	$27.99	$28.00	$28.00
Purchase #3	$99.82	3.640%	$103.4534	$103.45	$103.45	$103.50
Purchase #4	$40.94	13.832%	$46.6028	$46.60	$46.60	$46.60
Purchase #5	$184.25	12.267%	$206.8519	$206.85	$206.85	$206.90
Purchase #6	$55.68	6.388%	$59.2368	$59.24	$59.25	$59.20
Purchase #7	$40.48	11.323%	$45.0636	$45.06	$45.05	$45.10
7 purchase totals =	$662.34		$732.4854	$732.48	$732.50	$732.60