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	$44.90	4.591%	$46.9614	$46.96	$46.95	$47.00
Purchase #2	$25.70	7.390%	$27.5992	$27.60	$27.60	$27.60
Purchase #3	$33.93	11.597%	$37.8649	$37.86	$37.85	$37.90
Purchase #4	$202.81	13.738%	$230.672	$230.67	$230.65	$230.70
Purchase #5	$146.95	10.658%	$162.6119	$162.61	$162.60	$162.60
Purchase #6	$53.39	11.411%	$59.4823	$59.48	$59.50	$59.50
Purchase #7	$210.89	12.265%	$236.7557	$236.76	$236.75	$236.80
7 purchase totals =	$718.57		$801.9474	$801.94	$801.90	$802.10