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	$144.77	7.665%	$155.8666	$155.87	$155.85	$155.90
Purchase #2	$165.92	11.837%	$185.56	$185.56	$185.55	$185.60
Purchase #3	$154.40	10.799%	$171.0737	$171.07	$171.05	$171.10
Purchase #4	$240.99	12.707%	$271.6126	$271.61	$271.60	$271.60
Purchase #5	$24.68	11.246%	$27.4555	$27.46	$27.45	$27.50
Purchase #6	$113.50	9.461%	$124.2382	$124.24	$124.25	$124.20
Purchase #7	$112.46	13.667%	$127.8299	$127.83	$127.85	$127.80
7 purchase totals =	$956.72		$1,063.6365	$1,063.64	$1,063.60	$1,063.70