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	$247.35	11.116%	$274.8454	$274.85	$274.85	$274.80
Purchase #2	$97.73	3.606%	$101.2541	$101.25	$101.25	$101.30
Purchase #3	$189.83	8.320%	$205.6239	$205.62	$205.60	$205.60
Purchase #4	$143.78	10.181%	$158.4182	$158.42	$158.40	$158.40
Purchase #5	$85.30	6.589%	$90.9204	$90.92	$90.90	$90.90
Purchase #6	$209.69	12.608%	$236.1277	$236.13	$236.15	$236.10
Purchase #7	$147.28	11.554%	$164.2967	$164.30	$164.30	$164.30
7 purchase totals =	$1,120.96		$1,231.4864	$1,231.49	$1,231.45	$1,231.40