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	$152.62	13.404%	$173.0772	$173.08	$173.10	$173.10
Purchase #2	$160.43	12.783%	$180.9378	$180.94	$180.95	$180.90
Purchase #3	$141.34	13.453%	$160.3545	$160.35	$160.35	$160.40
Purchase #4	$120.68	4.819%	$126.4956	$126.50	$126.50	$126.50
Purchase #5	$207.50	5.164%	$218.2153	$218.22	$218.20	$218.20
Purchase #6	$84.27	7.514%	$90.602	$90.60	$90.60	$90.60
Purchase #7	$139.70	9.847%	$153.4563	$153.46	$153.45	$153.50
7 purchase totals =	$1,006.54		$1,103.1387	$1,103.15	$1,103.15	$1,103.20