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	$158.39	5.342%	$166.8512	$166.85	$166.85	$166.90
Purchase #2	$192.41	11.468%	$214.4756	$214.48	$214.50	$214.50
Purchase #3	$27.30	5.401%	$28.7745	$28.77	$28.75	$28.80
Purchase #4	$222.98	8.248%	$241.3714	$241.37	$241.35	$241.40
Purchase #5	$43.83	3.425%	$45.3312	$45.33	$45.35	$45.30
Purchase #6	$139.46	13.842%	$158.7641	$158.76	$158.75	$158.80
Purchase #7	$19.60	4.222%	$20.4275	$20.43	$20.45	$20.40
7 purchase totals =	$803.97		$875.9955	$875.99	$876.00	$876.10