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	$52.57	12.506%	$59.1444	$59.14	$59.15	$59.10
Purchase #2	$121.42	13.378%	$137.6636	$137.66	$137.65	$137.70
Purchase #3	$160.85	7.815%	$173.4204	$173.42	$173.40	$173.40
Purchase #4	$42.63	6.390%	$45.3541	$45.35	$45.35	$45.40
Purchase #5	$132.78	7.138%	$142.2578	$142.26	$142.25	$142.30
Purchase #6	$144.74	6.874%	$154.6894	$154.69	$154.70	$154.70
Purchase #7	$77.62	11.434%	$86.4951	$86.50	$86.50	$86.50
7 purchase totals =	$732.61		$799.0248	$799.02	$799.00	$799.10