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	$188.47	4.186%	$196.3594	$196.36	$196.35	$196.40
Purchase #2	$240.63	10.466%	$265.8143	$265.81	$265.80	$265.80
Purchase #3	$115.70	3.436%	$119.6755	$119.68	$119.70	$119.70
Purchase #4	$127.80	7.801%	$137.7697	$137.77	$137.75	$137.80
Purchase #5	$13.37	7.503%	$14.3732	$14.37	$14.35	$14.40
Purchase #6	$180.44	10.557%	$199.4891	$199.49	$199.50	$199.50
Purchase #7	$105.67	5.163%	$111.1257	$111.13	$111.15	$111.10
7 purchase totals =	$972.08		$1,044.6069	$1,044.61	$1,044.60	$1,044.70