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	$32.85	9.653%	$36.021	$36.02	$36.00	$36.00
Purchase #2	$85.38	6.222%	$90.6923	$90.69	$90.70	$90.70
Purchase #3	$74.47	6.525%	$79.3292	$79.33	$79.35	$79.30
Purchase #4	$106.69	4.441%	$111.4281	$111.43	$111.45	$111.40
Purchase #5	$66.54	7.591%	$71.5911	$71.59	$71.60	$71.60
Purchase #6	$136.85	4.834%	$143.4653	$143.47	$143.45	$143.50
Purchase #7	$88.41	4.553%	$92.4353	$92.44	$92.45	$92.40
7 purchase totals =	$591.19		$624.9623	$624.97	$625.00	$624.90