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	$32.28	9.110%	$35.2207	$35.22	$35.20	$35.20
Purchase #2	$78.50	3.580%	$81.3103	$81.31	$81.30	$81.30
Purchase #3	$116.67	4.859%	$122.339	$122.34	$122.35	$122.30
Purchase #4	$59.59	13.214%	$67.4642	$67.46	$67.45	$67.50
Purchase #5	$214.72	8.814%	$233.6454	$233.65	$233.65	$233.60
Purchase #6	$230.40	11.494%	$256.8822	$256.88	$256.90	$256.90
Purchase #7	$157.88	6.153%	$167.5944	$167.59	$167.60	$167.60
7 purchase totals =	$890.04		$964.4562	$964.45	$964.45	$964.40