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	$154.66	4.495%	$161.612	$161.61	$161.60	$161.60
Purchase #2	$211.71	12.665%	$238.5231	$238.52	$238.50	$238.50
Purchase #3	$160.80	5.613%	$169.8257	$169.83	$169.85	$169.80
Purchase #4	$128.90	3.842%	$133.8523	$133.85	$133.85	$133.90
Purchase #5	$235.35	9.281%	$257.1928	$257.19	$257.20	$257.20
Purchase #6	$90.47	5.611%	$95.5463	$95.55	$95.55	$95.50
Purchase #7	$99.34	12.211%	$111.4704	$111.47	$111.45	$111.50
7 purchase totals =	$1,081.23		$1,168.0226	$1,168.02	$1,168.00	$1,168.00