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	$118.95	3.143%	$122.6886	$122.69	$122.70	$122.70
Purchase #2	$189.65	10.873%	$210.2706	$210.27	$210.25	$210.30
Purchase #3	$47.28	12.242%	$53.068	$53.07	$53.05	$53.10
Purchase #4	$132.59	6.778%	$141.577	$141.58	$141.60	$141.60
Purchase #5	$215.67	13.262%	$244.2722	$244.27	$244.25	$244.30
Purchase #6	$95.56	3.762%	$99.155	$99.16	$99.15	$99.20
Purchase #7	$86.40	3.194%	$89.1596	$89.16	$89.15	$89.20
7 purchase totals =	$886.10		$960.1910	$960.20	$960.15	$960.40