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	$141.99	3.561%	$147.0463	$147.05	$147.05	$147.00
Purchase #2	$212.70	8.233%	$230.2116	$230.21	$230.20	$230.20
Purchase #3	$133.47	4.533%	$139.5202	$139.52	$139.50	$139.50
Purchase #4	$187.47	13.662%	$213.0822	$213.08	$213.10	$213.10
Purchase #5	$95.47	10.629%	$105.6175	$105.62	$105.60	$105.60
Purchase #6	$172.71	13.606%	$196.2089	$196.21	$196.20	$196.20
Purchase #7	$180.29	6.393%	$191.8159	$191.82	$191.80	$191.80
7 purchase totals =	$1,124.10		$1,223.5026	$1,223.51	$1,223.45	$1,223.40