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	$7.39	4.728%	$7.7394	$7.74	$7.75	$7.70
Purchase #2	$127.61	11.335%	$142.0746	$142.07	$142.05	$142.10
Purchase #3	$207.61	4.588%	$217.1351	$217.14	$217.15	$217.10
Purchase #4	$29.69	8.697%	$32.2721	$32.27	$32.25	$32.30
Purchase #5	$54.47	3.522%	$56.3884	$56.39	$56.40	$56.40
Purchase #6	$66.52	9.764%	$73.015	$73.02	$73.00	$73.00
Purchase #7	$173.67	9.809%	$190.7053	$190.71	$190.70	$190.70
7 purchase totals =	$666.96		$719.3299	$719.34	$719.30	$719.30