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	$87.79	4.420%	$91.6703	$91.67	$91.65	$91.70
Purchase #2	$21.31	8.208%	$23.0591	$23.06	$23.05	$23.10
Purchase #3	$132.92	4.511%	$138.916	$138.92	$138.90	$138.90
Purchase #4	$5.25	5.129%	$5.5193	$5.52	$5.50	$5.50
Purchase #5	$40.94	11.113%	$45.4897	$45.49	$45.50	$45.50
Purchase #6	$105.73	5.218%	$111.247	$111.25	$111.25	$111.20
Purchase #7	$39.58	7.321%	$42.4777	$42.48	$42.50	$42.50
7 purchase totals =	$433.52		$458.3791	$458.39	$458.35	$458.40