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	$153.39	8.520%	$166.4588	$166.46	$166.45	$166.50
Purchase #2	$78.27	4.672%	$81.9268	$81.93	$81.95	$81.90
Purchase #3	$90.28	6.762%	$96.3847	$96.38	$96.40	$96.40
Purchase #4	$132.29	5.249%	$139.2339	$139.23	$139.25	$139.20
Purchase #5	$22.45	6.139%	$23.8282	$23.83	$23.85	$23.80
Purchase #6	$37.56	12.598%	$42.2918	$42.29	$42.30	$42.30
Purchase #7	$96.32	3.231%	$99.4321	$99.43	$99.45	$99.40
7 purchase totals =	$610.56		$649.5563	$649.55	$649.65	$649.50