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	$228.25	6.692%	$243.5245	$243.52	$243.50	$243.50
Purchase #2	$221.44	9.231%	$241.8811	$241.88	$241.90	$241.90
Purchase #3	$54.66	4.600%	$57.1744	$57.17	$57.15	$57.20
Purchase #4	$145.93	8.323%	$158.0758	$158.08	$158.10	$158.10
Purchase #5	$131.62	4.847%	$137.9996	$138.00	$138.00	$138.00
Purchase #6	$145.85	4.796%	$152.845	$152.85	$152.85	$152.80
Purchase #7	$73.91	6.345%	$78.5996	$78.60	$78.60	$78.60
7 purchase totals =	$1,001.66		$1,070.1000	$1,070.10	$1,070.10	$1,070.10