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	$54.38	8.590%	$59.0512	$59.05	$59.05	$59.10
Purchase #2	$245.31	5.290%	$258.2869	$258.29	$258.30	$258.30
Purchase #3	$10.92	9.380%	$11.9443	$11.94	$11.95	$11.90
Purchase #4	$18.30	8.570%	$19.8683	$19.87	$19.85	$19.90
Purchase #5	$176.37	6.356%	$187.5801	$187.58	$187.60	$187.60
Purchase #6	$34.32	13.524%	$38.9614	$38.96	$38.95	$39.00
Purchase #7	$161.29	9.488%	$176.5932	$176.59	$176.60	$176.60
7 purchase totals =	$700.89		$752.2854	$752.28	$752.30	$752.40