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	$43.80	5.458%	$46.1906	$46.19	$46.20	$46.20
Purchase #2	$90.92	11.467%	$101.3458	$101.35	$101.35	$101.30
Purchase #3	$49.36	4.629%	$51.6449	$51.64	$51.65	$51.60
Purchase #4	$165.96	9.416%	$181.5868	$181.59	$181.60	$181.60
Purchase #5	$17.98	3.199%	$18.5552	$18.56	$18.55	$18.60
Purchase #6	$70.30	12.176%	$78.8597	$78.86	$78.85	$78.90
Purchase #7	$116.62	13.278%	$132.1048	$132.10	$132.10	$132.10
7 purchase totals =	$554.94		$610.2878	$610.29	$610.30	$610.30