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	$228.28	11.828%	$255.281	$255.28	$255.30	$255.30
Purchase #2	$202.99	9.304%	$221.8762	$221.88	$221.90	$221.90
Purchase #3	$20.60	3.186%	$21.2563	$21.26	$21.25	$21.30
Purchase #4	$24.55	5.297%	$25.8504	$25.85	$25.85	$25.90
Purchase #5	$239.75	4.853%	$251.3851	$251.39	$251.40	$251.40
Purchase #6	$172.83	7.257%	$185.3723	$185.37	$185.35	$185.40
Purchase #7	$105.74	4.816%	$110.8324	$110.83	$110.85	$110.80
7 purchase totals =	$994.74		$1,071.8537	$1,071.86	$1,071.90	$1,072.00