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	$137.62	7.485%	$147.9209	$147.92	$147.90	$147.90
Purchase #2	$91.82	4.103%	$95.5874	$95.59	$95.60	$95.60
Purchase #3	$24.60	3.512%	$25.464	$25.46	$25.45	$25.50
Purchase #4	$38.77	3.365%	$40.0746	$40.07	$40.05	$40.10
Purchase #5	$19.36	4.197%	$20.1725	$20.17	$20.15	$20.20
Purchase #6	$125.37	9.753%	$137.5973	$137.60	$137.60	$137.60
Purchase #7	$11.91	7.796%	$12.8385	$12.84	$12.85	$12.80
7 purchase totals =	$449.45		$479.6552	$479.65	$479.60	$479.70