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	$82.50	3.377%	$85.286	$85.29	$85.30	$85.30
Purchase #2	$107.34	3.734%	$111.3481	$111.35	$111.35	$111.30
Purchase #3	$76.57	5.792%	$81.0049	$81.00	$81.00	$81.00
Purchase #4	$206.70	11.867%	$231.2291	$231.23	$231.25	$231.20
Purchase #5	$47.88	13.600%	$54.3917	$54.39	$54.40	$54.40
Purchase #6	$61.30	8.335%	$66.4094	$66.41	$66.40	$66.40
Purchase #7	$111.48	13.707%	$126.7606	$126.76	$126.75	$126.80
7 purchase totals =	$693.77		$756.4298	$756.43	$756.45	$756.40