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	$241.39	10.444%	$266.6008	$266.60	$266.60	$266.60
Purchase #2	$244.72	4.157%	$254.893	$254.89	$254.90	$254.90
Purchase #3	$127.81	6.686%	$136.3554	$136.36	$136.35	$136.40
Purchase #4	$127.54	13.436%	$144.6763	$144.68	$144.70	$144.70
Purchase #5	$58.64	6.575%	$62.4956	$62.50	$62.50	$62.50
Purchase #6	$54.67	6.617%	$58.2875	$58.29	$58.30	$58.30
Purchase #7	$218.75	11.301%	$243.4709	$243.47	$243.45	$243.50
7 purchase totals =	$1,073.52		$1,166.7795	$1,166.79	$1,166.80	$1,166.90