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	$45.34	5.788%	$47.9643	$47.96	$47.95	$48.00
Purchase #2	$186.49	4.246%	$194.4084	$194.41	$194.40	$194.40
Purchase #3	$181.33	10.387%	$200.1647	$200.16	$200.15	$200.20
Purchase #4	$105.28	12.774%	$118.7285	$118.73	$118.75	$118.70
Purchase #5	$138.92	9.309%	$151.8521	$151.85	$151.85	$151.90
Purchase #6	$94.93	5.398%	$100.0543	$100.05	$100.05	$100.10
Purchase #7	$246.41	3.551%	$255.16	$255.16	$255.15	$255.20
7 purchase totals =	$998.70		$1,068.3323	$1,068.32	$1,068.30	$1,068.50