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	$106.54	9.421%	$116.5771	$116.58	$116.60	$116.60
Purchase #2	$56.83	6.278%	$60.3978	$60.40	$60.40	$60.40
Purchase #3	$71.69	6.114%	$76.0731	$76.07	$76.05	$76.10
Purchase #4	$188.89	4.178%	$196.7818	$196.78	$196.80	$196.80
Purchase #5	$167.42	3.423%	$173.1508	$173.15	$173.15	$173.20
Purchase #6	$227.58	11.607%	$253.9952	$254.00	$254.00	$254.00
Purchase #7	$17.61	4.847%	$18.4636	$18.46	$18.45	$18.50
7 purchase totals =	$836.56		$895.4394	$895.44	$895.45	$895.60