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	$128.39	11.723%	$143.4412	$143.44	$143.45	$143.40
Purchase #2	$147.25	3.680%	$152.6688	$152.67	$152.65	$152.70
Purchase #3	$204.37	10.811%	$226.4644	$226.46	$226.45	$226.50
Purchase #4	$103.83	7.569%	$111.6889	$111.69	$111.70	$111.70
Purchase #5	$58.72	12.346%	$65.9696	$65.97	$65.95	$66.00
Purchase #6	$248.59	7.192%	$266.4686	$266.47	$266.45	$266.50
Purchase #7	$153.93	7.845%	$166.0058	$166.01	$166.00	$166.00
7 purchase totals =	$1,045.08		$1,132.7073	$1,132.71	$1,132.65	$1,132.80