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	$145.76	5.225%	$153.376	$153.38	$153.40	$153.40
Purchase #2	$90.27	5.356%	$95.1049	$95.10	$95.10	$95.10
Purchase #3	$193.86	4.685%	$202.9423	$202.94	$202.95	$202.90
Purchase #4	$57.69	13.247%	$65.3322	$65.33	$65.35	$65.30
Purchase #5	$116.49	9.234%	$127.2467	$127.25	$127.25	$127.20
Purchase #6	$230.83	10.871%	$255.9235	$255.92	$255.90	$255.90
Purchase #7	$40.28	5.174%	$42.3641	$42.36	$42.35	$42.40
7 purchase totals =	$875.18		$942.2897	$942.28	$942.30	$942.20