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	$158.97	9.126%	$173.4776	$173.48	$173.50	$173.50
Purchase #2	$118.64	11.383%	$132.1448	$132.14	$132.15	$132.10
Purchase #3	$96.55	4.190%	$100.5954	$100.60	$100.60	$100.60
Purchase #4	$98.33	6.307%	$104.5317	$104.53	$104.55	$104.50
Purchase #5	$246.83	12.680%	$278.128	$278.13	$278.15	$278.10
Purchase #6	$229.89	11.238%	$255.725	$255.73	$255.75	$255.70
Purchase #7	$247.97	5.547%	$261.7249	$261.72	$261.70	$261.70
7 purchase totals =	$1,197.18		$1,306.3274	$1,306.33	$1,306.40	$1,306.20