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	$100.90	4.814%	$105.7573	$105.76	$105.75	$105.80
Purchase #2	$132.32	4.597%	$138.4028	$138.40	$138.40	$138.40
Purchase #3	$135.94	10.775%	$150.5875	$150.59	$150.60	$150.60
Purchase #4	$148.94	10.520%	$164.6085	$164.61	$164.60	$164.60
Purchase #5	$141.78	5.239%	$149.2079	$149.21	$149.20	$149.20
Purchase #6	$127.57	5.168%	$134.1628	$134.16	$134.15	$134.20
Purchase #7	$228.33	12.433%	$256.7183	$256.72	$256.70	$256.70
7 purchase totals =	$1,015.78		$1,099.4451	$1,099.45	$1,099.40	$1,099.50