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	$49.69	9.147%	$54.2351	$54.24	$54.25	$54.20
Purchase #2	$160.35	11.303%	$178.4744	$178.47	$178.45	$178.50
Purchase #3	$77.43	5.747%	$81.8799	$81.88	$81.90	$81.90
Purchase #4	$170.51	4.618%	$178.3842	$178.38	$178.40	$178.40
Purchase #5	$235.98	8.152%	$255.2171	$255.22	$255.20	$255.20
Purchase #6	$173.97	12.711%	$196.0833	$196.08	$196.10	$196.10
Purchase #7	$86.51	13.106%	$97.848	$97.85	$97.85	$97.80
7 purchase totals =	$954.44		$1,042.1220	$1,042.12	$1,042.15	$1,042.10