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	$142.51	8.702%	$154.9112	$154.91	$154.90	$154.90
Purchase #2	$63.48	13.521%	$72.0631	$72.06	$72.05	$72.10
Purchase #3	$205.72	4.210%	$214.3808	$214.38	$214.40	$214.40
Purchase #4	$25.35	3.844%	$26.3245	$26.32	$26.30	$26.30
Purchase #5	$148.50	4.553%	$155.2612	$155.26	$155.25	$155.30
Purchase #6	$191.89	11.468%	$213.8959	$213.90	$213.90	$213.90
Purchase #7	$45.46	11.297%	$50.5956	$50.60	$50.60	$50.60
7 purchase totals =	$822.91		$887.4323	$887.43	$887.40	$887.50