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	$240.50	6.272%	$255.5842	$255.58	$255.60	$255.60
Purchase #2	$63.49	5.647%	$67.0753	$67.08	$67.10	$67.10
Purchase #3	$132.43	13.850%	$150.7716	$150.77	$150.75	$150.80
Purchase #4	$50.33	7.321%	$54.0147	$54.01	$54.00	$54.00
Purchase #5	$63.57	4.369%	$66.3474	$66.35	$66.35	$66.30
Purchase #6	$98.39	10.379%	$108.6019	$108.60	$108.60	$108.60
Purchase #7	$22.72	5.814%	$24.0409	$24.04	$24.05	$24.00
7 purchase totals =	$671.43		$726.4360	$726.43	$726.45	$726.40