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	$111.43	5.318%	$117.3558	$117.36	$117.35	$117.40
Purchase #2	$215.87	11.707%	$241.1419	$241.14	$241.15	$241.10
Purchase #3	$50.40	10.248%	$55.565	$55.57	$55.55	$55.60
Purchase #4	$116.32	9.519%	$127.3925	$127.39	$127.40	$127.40
Purchase #5	$237.49	5.809%	$251.2858	$251.29	$251.30	$251.30
Purchase #6	$61.94	13.811%	$70.4945	$70.49	$70.50	$70.50
Purchase #7	$184.65	13.380%	$209.3562	$209.36	$209.35	$209.40
7 purchase totals =	$978.10		$1,072.5917	$1,072.60	$1,072.60	$1,072.70