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	$148.72	9.105%	$162.261	$162.26	$162.25	$162.30
Purchase #2	$211.26	5.769%	$223.4476	$223.45	$223.45	$223.40
Purchase #3	$216.72	10.812%	$240.1518	$240.15	$240.15	$240.20
Purchase #4	$111.62	13.555%	$126.7501	$126.75	$126.75	$126.80
Purchase #5	$143.52	9.677%	$157.4084	$157.41	$157.40	$157.40
Purchase #6	$128.76	8.309%	$139.4587	$139.46	$139.45	$139.50
Purchase #7	$139.92	5.360%	$147.4197	$147.42	$147.40	$147.40
7 purchase totals =	$1,100.52		$1,196.8973	$1,196.90	$1,196.85	$1,197.00