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	$31.28	3.836%	$32.4799	$32.48	$32.50	$32.50
Purchase #2	$55.25	10.264%	$60.9209	$60.92	$60.90	$60.90
Purchase #3	$54.59	9.643%	$59.8541	$59.85	$59.85	$59.90
Purchase #4	$20.94	11.381%	$23.3232	$23.32	$23.30	$23.30
Purchase #5	$211.66	6.598%	$225.6253	$225.63	$225.65	$225.60
Purchase #6	$119.86	8.820%	$130.4317	$130.43	$130.45	$130.40
Purchase #7	$197.42	12.571%	$222.2377	$222.24	$222.25	$222.20
7 purchase totals =	$691.00		$754.8728	$754.87	$754.90	$754.80