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	$45.52	6.530%	$48.4925	$48.49	$48.50	$48.50
Purchase #2	$207.85	6.661%	$221.6949	$221.69	$221.70	$221.70
Purchase #3	$194.34	11.388%	$216.4714	$216.47	$216.45	$216.50
Purchase #4	$162.94	5.419%	$171.7697	$171.77	$171.75	$171.80
Purchase #5	$170.87	4.788%	$179.0513	$179.05	$179.05	$179.10
Purchase #6	$38.66	7.156%	$41.4265	$41.43	$41.45	$41.40
Purchase #7	$177.51	4.286%	$185.1181	$185.12	$185.10	$185.10
7 purchase totals =	$997.69		$1,064.0244	$1,064.02	$1,064.00	$1,064.10