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	$100.60	4.813%	$105.4419	$105.44	$105.45	$105.40
Purchase #2	$172.55	3.394%	$178.4063	$178.41	$178.40	$178.40
Purchase #3	$212.34	6.458%	$226.0529	$226.05	$226.05	$226.10
Purchase #4	$86.89	13.176%	$98.3386	$98.34	$98.35	$98.30
Purchase #5	$249.62	7.845%	$269.2027	$269.20	$269.20	$269.20
Purchase #6	$19.64	9.226%	$21.452	$21.45	$21.45	$21.50
Purchase #7	$229.42	11.375%	$255.5165	$255.52	$255.50	$255.50
7 purchase totals =	$1,071.06		$1,154.4109	$1,154.41	$1,154.40	$1,154.40