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	$33.77	5.687%	$35.6905	$35.69	$35.70	$35.70
Purchase #2	$204.32	3.605%	$211.6857	$211.69	$211.70	$211.70
Purchase #3	$136.58	5.537%	$144.1424	$144.14	$144.15	$144.10
Purchase #4	$195.36	7.804%	$210.6059	$210.61	$210.60	$210.60
Purchase #5	$34.38	4.787%	$36.0258	$36.03	$36.05	$36.00
Purchase #6	$44.52	9.359%	$48.6866	$48.69	$48.70	$48.70
Purchase #7	$104.89	6.373%	$111.5746	$111.57	$111.55	$111.60
7 purchase totals =	$753.82		$798.4115	$798.42	$798.45	$798.40