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	$69.46	4.424%	$72.5329	$72.53	$72.55	$72.50
Purchase #2	$7.34	8.336%	$7.9519	$7.95	$7.95	$8.00
Purchase #3	$127.42	13.534%	$144.665	$144.67	$144.65	$144.70
Purchase #4	$89.32	12.381%	$100.3787	$100.38	$100.40	$100.40
Purchase #5	$117.82	10.785%	$130.5269	$130.53	$130.55	$130.50
Purchase #6	$244.43	6.397%	$260.0662	$260.07	$260.05	$260.10
Purchase #7	$17.83	11.359%	$19.8553	$19.86	$19.85	$19.90
7 purchase totals =	$673.62		$735.9769	$735.99	$736.00	$736.10