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	$181.90	4.462%	$190.0164	$190.02	$190.00	$190.00
Purchase #2	$228.73	11.258%	$254.4804	$254.48	$254.50	$254.50
Purchase #3	$121.79	13.730%	$138.5118	$138.51	$138.50	$138.50
Purchase #4	$50.49	8.621%	$54.8427	$54.84	$54.85	$54.80
Purchase #5	$174.42	9.321%	$190.6777	$190.68	$190.70	$190.70
Purchase #6	$222.39	12.497%	$250.1821	$250.18	$250.20	$250.20
Purchase #7	$240.44	6.841%	$256.8885	$256.89	$256.90	$256.90
7 purchase totals =	$1,220.16		$1,335.5996	$1,335.60	$1,335.65	$1,335.60