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	$111.55	13.476%	$126.5825	$126.58	$126.60	$126.60
Purchase #2	$17.98	6.342%	$19.1203	$19.12	$19.10	$19.10
Purchase #3	$149.54	7.541%	$160.8168	$160.82	$160.80	$160.80
Purchase #4	$137.41	11.569%	$153.307	$153.31	$153.30	$153.30
Purchase #5	$82.98	10.102%	$91.3626	$91.36	$91.35	$91.40
Purchase #6	$91.69	13.564%	$104.1268	$104.13	$104.15	$104.10
Purchase #7	$78.87	11.767%	$88.1506	$88.15	$88.15	$88.20
7 purchase totals =	$670.02		$743.4666	$743.47	$743.45	$743.50