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	$205.59	10.209%	$226.5787	$226.58	$226.60	$226.60
Purchase #2	$105.54	3.572%	$109.3099	$109.31	$109.30	$109.30
Purchase #3	$207.38	5.357%	$218.4893	$218.49	$218.50	$218.50
Purchase #4	$217.87	12.352%	$244.7813	$244.78	$244.80	$244.80
Purchase #5	$5.53	11.261%	$6.1527	$6.15	$6.15	$6.20
Purchase #6	$137.59	10.703%	$152.3163	$152.32	$152.30	$152.30
Purchase #7	$195.72	6.509%	$208.4594	$208.46	$208.45	$208.50
7 purchase totals =	$1,075.22		$1,166.0876	$1,166.09	$1,166.10	$1,166.20