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	$158.42	13.785%	$180.2582	$180.26	$180.25	$180.30
Purchase #2	$151.72	8.629%	$164.8119	$164.81	$164.80	$164.80
Purchase #3	$247.96	12.798%	$279.6939	$279.69	$279.70	$279.70
Purchase #4	$76.72	9.294%	$83.8504	$83.85	$83.85	$83.90
Purchase #5	$49.88	10.195%	$54.9653	$54.97	$54.95	$55.00
Purchase #6	$173.90	6.475%	$185.16	$185.16	$185.15	$185.20
Purchase #7	$195.35	10.458%	$215.7797	$215.78	$215.80	$215.80
7 purchase totals =	$1,053.95		$1,164.5194	$1,164.52	$1,164.50	$1,164.70