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	$23.48	5.137%	$24.6862	$24.69	$24.70	$24.70
Purchase #2	$31.62	4.830%	$33.1472	$33.15	$33.15	$33.10
Purchase #3	$70.83	13.839%	$80.6322	$80.63	$80.65	$80.60
Purchase #4	$208.85	5.846%	$221.0594	$221.06	$221.05	$221.10
Purchase #5	$151.35	10.790%	$167.6807	$167.68	$167.70	$167.70
Purchase #6	$33.81	11.163%	$37.5842	$37.58	$37.60	$37.60
Purchase #7	$168.96	6.265%	$179.5453	$179.55	$179.55	$179.50
7 purchase totals =	$688.90		$744.3352	$744.34	$744.40	$744.30