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	$157.32	10.532%	$173.8889	$173.89	$173.90	$173.90
Purchase #2	$12.98	5.449%	$13.6873	$13.69	$13.70	$13.70
Purchase #3	$176.31	13.451%	$200.0255	$200.03	$200.05	$200.00
Purchase #4	$155.56	4.706%	$162.8807	$162.88	$162.90	$162.90
Purchase #5	$113.72	5.829%	$120.3487	$120.35	$120.35	$120.30
Purchase #6	$11.41	8.594%	$12.3906	$12.39	$12.40	$12.40
Purchase #7	$51.75	6.829%	$55.284	$55.28	$55.30	$55.30
7 purchase totals =	$679.05		$738.5057	$738.51	$738.60	$738.50