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	$98.55	6.808%	$105.2593	$105.26	$105.25	$105.30
Purchase #2	$213.82	7.535%	$229.9313	$229.93	$229.95	$229.90
Purchase #3	$10.42	8.519%	$11.3077	$11.31	$11.30	$11.30
Purchase #4	$46.87	12.543%	$52.7489	$52.75	$52.75	$52.70
Purchase #5	$152.26	7.818%	$164.1637	$164.16	$164.15	$164.20
Purchase #6	$107.32	3.464%	$111.0376	$111.04	$111.05	$111.00
Purchase #7	$127.72	3.382%	$132.0395	$132.04	$132.05	$132.00
7 purchase totals =	$756.96		$806.4880	$806.49	$806.50	$806.40