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	$247.53	6.407%	$263.3892	$263.39	$263.40	$263.40
Purchase #2	$76.56	11.486%	$85.3537	$85.35	$85.35	$85.40
Purchase #3	$111.99	10.121%	$123.3245	$123.32	$123.30	$123.30
Purchase #4	$82.88	9.500%	$90.7536	$90.75	$90.75	$90.80
Purchase #5	$34.58	13.304%	$39.1805	$39.18	$39.20	$39.20
Purchase #6	$183.67	13.492%	$208.4508	$208.45	$208.45	$208.50
Purchase #7	$179.55	13.736%	$204.213	$204.21	$204.20	$204.20
7 purchase totals =	$916.76		$1,014.6653	$1,014.65	$1,014.65	$1,014.80