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	$52.45	3.302%	$54.1819	$54.18	$54.20	$54.20
Purchase #2	$134.76	12.502%	$151.6077	$151.61	$151.60	$151.60
Purchase #3	$175.30	5.503%	$184.9468	$184.95	$184.95	$184.90
Purchase #4	$50.55	3.357%	$52.247	$52.25	$52.25	$52.20
Purchase #5	$13.94	4.801%	$14.6093	$14.61	$14.60	$14.60
Purchase #6	$36.80	5.834%	$38.9469	$38.95	$38.95	$38.90
Purchase #7	$154.43	10.625%	$170.8382	$170.84	$170.85	$170.80
7 purchase totals =	$618.23		$667.3778	$667.39	$667.40	$667.20