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	$224.43	7.819%	$241.9782	$241.98	$242.00	$242.00
Purchase #2	$118.51	3.317%	$122.441	$122.44	$122.45	$122.40
Purchase #3	$30.52	8.837%	$33.2171	$33.22	$33.20	$33.20
Purchase #4	$24.59	12.288%	$27.6116	$27.61	$27.60	$27.60
Purchase #5	$118.52	7.301%	$127.1731	$127.17	$127.15	$127.20
Purchase #6	$41.56	4.570%	$43.4593	$43.46	$43.45	$43.50
Purchase #7	$248.88	10.568%	$275.1816	$275.18	$275.20	$275.20
7 purchase totals =	$807.01		$871.0619	$871.06	$871.05	$871.10