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	$151.55	3.343%	$156.6163	$156.62	$156.60	$156.60
Purchase #2	$66.39	5.544%	$70.0707	$70.07	$70.05	$70.10
Purchase #3	$104.47	5.143%	$109.8429	$109.84	$109.85	$109.80
Purchase #4	$6.70	10.451%	$7.4002	$7.40	$7.40	$7.40
Purchase #5	$154.59	9.616%	$169.4554	$169.46	$169.45	$169.50
Purchase #6	$92.61	4.698%	$96.9608	$96.96	$96.95	$97.00
Purchase #7	$99.25	12.168%	$111.3267	$111.33	$111.35	$111.30
7 purchase totals =	$675.56		$721.6730	$721.68	$721.65	$721.70