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	$144.92	6.545%	$154.405	$154.41	$154.40	$154.40
Purchase #2	$140.51	11.313%	$156.4059	$156.41	$156.40	$156.40
Purchase #3	$126.60	4.409%	$132.1818	$132.18	$132.20	$132.20
Purchase #4	$126.72	13.312%	$143.589	$143.59	$143.60	$143.60
Purchase #5	$50.27	13.495%	$57.0539	$57.05	$57.05	$57.10
Purchase #6	$18.28	13.573%	$20.7611	$20.76	$20.75	$20.80
Purchase #7	$85.82	11.172%	$95.4078	$95.41	$95.40	$95.40
7 purchase totals =	$693.12		$759.8045	$759.81	$759.80	$759.90