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	$66.70	11.854%	$74.6066	$74.61	$74.60	$74.60
Purchase #2	$134.50	12.642%	$151.5035	$151.50	$151.50	$151.50
Purchase #3	$13.89	11.184%	$15.4435	$15.44	$15.45	$15.40
Purchase #4	$52.79	6.276%	$56.1031	$56.10	$56.10	$56.10
Purchase #5	$57.83	12.534%	$65.0784	$65.08	$65.10	$65.10
Purchase #6	$156.65	3.408%	$161.9886	$161.99	$162.00	$162.00
Purchase #7	$57.25	3.281%	$59.1284	$59.13	$59.15	$59.10
7 purchase totals =	$539.61		$583.8521	$583.85	$583.90	$583.80