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	$54.64	8.461%	$59.2631	$59.26	$59.25	$59.30
Purchase #2	$221.82	8.829%	$241.4045	$241.40	$241.40	$241.40
Purchase #3	$30.53	13.333%	$34.6006	$34.60	$34.60	$34.60
Purchase #4	$61.26	4.138%	$63.7949	$63.79	$63.80	$63.80
Purchase #5	$47.38	4.219%	$49.379	$49.38	$49.40	$49.40
Purchase #6	$77.75	10.267%	$85.7326	$85.73	$85.75	$85.70
Purchase #7	$88.35	13.336%	$100.1324	$100.13	$100.15	$100.10
7 purchase totals =	$581.73		$634.3071	$634.29	$634.35	$634.30