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	$153.38	5.844%	$162.3435	$162.34	$162.35	$162.30
Purchase #2	$37.65	4.431%	$39.3183	$39.32	$39.30	$39.30
Purchase #3	$50.55	9.591%	$55.3983	$55.40	$55.40	$55.40
Purchase #4	$25.39	8.105%	$27.4479	$27.45	$27.45	$27.40
Purchase #5	$249.48	10.487%	$275.643	$275.64	$275.65	$275.60
Purchase #6	$105.47	4.246%	$109.9483	$109.95	$109.95	$109.90
Purchase #7	$202.60	10.783%	$224.4464	$224.45	$224.45	$224.40
7 purchase totals =	$824.52		$894.5457	$894.55	$894.55	$894.30