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	$146.64	9.366%	$160.3743	$160.37	$160.35	$160.40
Purchase #2	$27.91	12.230%	$31.3234	$31.32	$31.30	$31.30
Purchase #3	$35.85	4.585%	$37.4937	$37.49	$37.50	$37.50
Purchase #4	$90.35	9.636%	$99.0561	$99.06	$99.05	$99.10
Purchase #5	$145.43	6.411%	$154.7535	$154.75	$154.75	$154.80
Purchase #6	$65.55	10.305%	$72.3049	$72.30	$72.30	$72.30
Purchase #7	$55.96	13.861%	$63.7166	$63.72	$63.70	$63.70
7 purchase totals =	$567.69		$619.0225	$619.01	$618.95	$619.10