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	$223.38	11.527%	$249.129	$249.13	$249.15	$249.10
Purchase #2	$62.45	4.439%	$65.2222	$65.22	$65.20	$65.20
Purchase #3	$162.86	13.476%	$184.807	$184.81	$184.80	$184.80
Purchase #4	$116.38	10.562%	$128.6721	$128.67	$128.65	$128.70
Purchase #5	$125.47	5.689%	$132.608	$132.61	$132.60	$132.60
Purchase #6	$41.33	10.222%	$45.5548	$45.55	$45.55	$45.60
Purchase #7	$196.36	6.163%	$208.4617	$208.46	$208.45	$208.50
7 purchase totals =	$928.23		$1,014.4548	$1,014.45	$1,014.40	$1,014.50