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	$65.55	5.585%	$69.211	$69.21	$69.20	$69.20
Purchase #2	$146.46	6.565%	$156.0751	$156.08	$156.10	$156.10
Purchase #3	$117.86	10.605%	$130.3591	$130.36	$130.35	$130.40
Purchase #4	$193.72	6.205%	$205.7403	$205.74	$205.75	$205.70
Purchase #5	$100.45	4.419%	$104.8889	$104.89	$104.90	$104.90
Purchase #6	$84.94	6.401%	$90.377	$90.38	$90.40	$90.40
Purchase #7	$241.52	7.789%	$260.332	$260.33	$260.35	$260.30
7 purchase totals =	$950.50		$1,016.9834	$1,016.99	$1,017.05	$1,017.00