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	$247.56	6.102%	$262.6661	$262.67	$262.65	$262.70
Purchase #2	$228.93	12.721%	$258.0522	$258.05	$258.05	$258.10
Purchase #3	$197.79	12.597%	$222.7056	$222.71	$222.70	$222.70
Purchase #4	$140.31	9.127%	$153.1161	$153.12	$153.10	$153.10
Purchase #5	$99.92	4.845%	$104.7611	$104.76	$104.75	$104.80
Purchase #6	$24.45	4.764%	$25.6148	$25.61	$25.60	$25.60
Purchase #7	$94.88	6.267%	$100.8261	$100.83	$100.85	$100.80
7 purchase totals =	$1,033.84		$1,127.7420	$1,127.75	$1,127.70	$1,127.80