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	$40.64	7.240%	$43.5823	$43.58	$43.60	$43.60
Purchase #2	$190.92	8.260%	$206.69	$206.69	$206.70	$206.70
Purchase #3	$9.72	4.230%	$10.1312	$10.13	$10.15	$10.10
Purchase #4	$72.59	13.563%	$82.4354	$82.44	$82.45	$82.40
Purchase #5	$225.68	11.434%	$251.4843	$251.48	$251.50	$251.50
Purchase #6	$224.73	11.698%	$251.0189	$251.02	$251.00	$251.00
Purchase #7	$51.27	6.838%	$54.7758	$54.78	$54.80	$54.80
7 purchase totals =	$815.55		$900.1179	$900.12	$900.20	$900.10