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	$199.74	12.684%	$225.075	$225.08	$225.10	$225.10
Purchase #2	$156.87	11.467%	$174.8583	$174.86	$174.85	$174.90
Purchase #3	$95.55	10.315%	$105.406	$105.41	$105.40	$105.40
Purchase #4	$136.38	11.229%	$151.6941	$151.69	$151.70	$151.70
Purchase #5	$43.70	11.177%	$48.5843	$48.58	$48.60	$48.60
Purchase #6	$164.76	9.479%	$180.3776	$180.38	$180.40	$180.40
Purchase #7	$166.42	4.140%	$173.3098	$173.31	$173.30	$173.30
7 purchase totals =	$963.42		$1,059.3051	$1,059.31	$1,059.35	$1,059.40