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	$31.82	7.405%	$34.1763	$34.18	$34.20	$34.20
Purchase #2	$118.71	7.295%	$127.3699	$127.37	$127.35	$127.40
Purchase #3	$40.80	13.795%	$46.4284	$46.43	$46.45	$46.40
Purchase #4	$170.45	6.320%	$181.2224	$181.22	$181.20	$181.20
Purchase #5	$95.35	6.461%	$101.5106	$101.51	$101.50	$101.50
Purchase #6	$127.98	11.677%	$142.9242	$142.92	$142.90	$142.90
Purchase #7	$205.40	11.381%	$228.7766	$228.78	$228.80	$228.80
7 purchase totals =	$790.51		$862.4084	$862.41	$862.40	$862.40