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	$147.64	5.515%	$155.7823	$155.78	$155.80	$155.80
Purchase #2	$230.65	10.585%	$255.0643	$255.06	$255.05	$255.10
Purchase #3	$76.83	12.345%	$86.3147	$86.31	$86.30	$86.30
Purchase #4	$117.57	11.554%	$131.154	$131.15	$131.15	$131.20
Purchase #5	$165.67	4.819%	$173.6536	$173.65	$173.65	$173.70
Purchase #6	$59.92	10.118%	$65.9827	$65.98	$66.00	$66.00
Purchase #7	$207.42	6.281%	$220.4481	$220.45	$220.45	$220.40
7 purchase totals =	$1,005.70		$1,088.3997	$1,088.38	$1,088.40	$1,088.50