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	$65.61	4.782%	$68.7475	$68.75	$68.75	$68.70
Purchase #2	$132.85	7.844%	$143.2708	$143.27	$143.25	$143.30
Purchase #3	$92.55	7.393%	$99.3922	$99.39	$99.40	$99.40
Purchase #4	$75.60	3.582%	$78.308	$78.31	$78.30	$78.30
Purchase #5	$39.78	6.276%	$42.2766	$42.28	$42.30	$42.30
Purchase #6	$117.95	6.476%	$125.5884	$125.59	$125.60	$125.60
Purchase #7	$111.54	13.505%	$126.6035	$126.60	$126.60	$126.60
7 purchase totals =	$635.88		$684.1870	$684.19	$684.20	$684.20