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	$160.99	7.404%	$172.9097	$172.91	$172.90	$172.90
Purchase #2	$29.68	3.471%	$30.7102	$30.71	$30.70	$30.70
Purchase #3	$98.34	13.412%	$111.5294	$111.53	$111.55	$111.50
Purchase #4	$47.28	12.599%	$53.2368	$53.24	$53.25	$53.20
Purchase #5	$128.42	4.824%	$134.615	$134.62	$134.60	$134.60
Purchase #6	$244.34	7.523%	$262.7217	$262.72	$262.70	$262.70
Purchase #7	$249.42	3.816%	$258.9379	$258.94	$258.95	$258.90
7 purchase totals =	$958.47		$1,024.6607	$1,024.67	$1,024.65	$1,024.50