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	$62.42	7.485%	$67.0921	$67.09	$67.10	$67.10
Purchase #2	$215.41	4.407%	$224.9031	$224.90	$224.90	$224.90
Purchase #3	$59.38	9.556%	$65.0544	$65.05	$65.05	$65.10
Purchase #4	$14.69	5.393%	$15.4822	$15.48	$15.50	$15.50
Purchase #5	$177.38	10.575%	$196.1379	$196.14	$196.15	$196.10
Purchase #6	$72.49	8.284%	$78.4951	$78.50	$78.50	$78.50
Purchase #7	$100.61	4.552%	$105.1898	$105.19	$105.20	$105.20
7 purchase totals =	$702.38		$752.3546	$752.35	$752.40	$752.40