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	$99.55	12.124%	$111.6194	$111.62	$111.60	$111.60
Purchase #2	$226.47	7.499%	$243.453	$243.45	$243.45	$243.50
Purchase #3	$52.90	9.808%	$58.0884	$58.09	$58.10	$58.10
Purchase #4	$23.69	5.474%	$24.9868	$24.99	$25.00	$25.00
Purchase #5	$205.60	13.614%	$233.5904	$233.59	$233.60	$233.60
Purchase #6	$31.30	3.570%	$32.4174	$32.42	$32.40	$32.40
Purchase #7	$18.53	11.663%	$20.6912	$20.69	$20.70	$20.70
7 purchase totals =	$658.04		$724.8466	$724.85	$724.85	$724.90