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	$221.53	3.688%	$229.7	$229.70	$229.70	$229.70
Purchase #2	$27.88	5.843%	$29.509	$29.51	$29.50	$29.50
Purchase #3	$250.28	11.750%	$279.6879	$279.69	$279.70	$279.70
Purchase #4	$238.29	11.849%	$266.525	$266.53	$266.55	$266.50
Purchase #5	$148.40	3.367%	$153.3966	$153.40	$153.40	$153.40
Purchase #6	$92.71	12.326%	$104.1374	$104.14	$104.15	$104.10
Purchase #7	$250.29	3.422%	$258.8549	$258.85	$258.85	$258.90
7 purchase totals =	$1,229.38		$1,321.8108	$1,321.82	$1,321.85	$1,321.80