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	$196.94	13.524%	$223.5742	$223.57	$223.55	$223.60
Purchase #2	$155.60	11.631%	$173.6978	$173.70	$173.70	$173.70
Purchase #3	$12.81	5.603%	$13.5277	$13.53	$13.55	$13.50
Purchase #4	$77.88	13.287%	$88.2279	$88.23	$88.25	$88.20
Purchase #5	$137.65	4.615%	$144.0025	$144.00	$144.00	$144.00
Purchase #6	$30.38	7.205%	$32.5689	$32.57	$32.55	$32.60
Purchase #7	$16.42	6.753%	$17.5288	$17.53	$17.55	$17.50
7 purchase totals =	$627.68		$693.1278	$693.13	$693.15	$693.10