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	$249.44	5.324%	$262.7202	$262.72	$262.70	$262.70
Purchase #2	$131.48	3.827%	$136.5117	$136.51	$136.50	$136.50
Purchase #3	$195.97	7.742%	$211.142	$211.14	$211.15	$211.10
Purchase #4	$41.52	12.778%	$46.8254	$46.83	$46.85	$46.80
Purchase #5	$11.32	11.376%	$12.6078	$12.61	$12.60	$12.60
Purchase #6	$47.45	10.695%	$52.5248	$52.52	$52.50	$52.50
Purchase #7	$117.68	5.605%	$124.276	$124.28	$124.30	$124.30
7 purchase totals =	$794.86		$846.6079	$846.61	$846.60	$846.50