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	$161.87	8.610%	$175.807	$175.81	$175.80	$175.80
Purchase #2	$117.27	5.376%	$123.5744	$123.57	$123.55	$123.60
Purchase #3	$180.54	10.452%	$199.41	$199.41	$199.40	$199.40
Purchase #4	$27.69	5.345%	$29.17	$29.17	$29.15	$29.20
Purchase #5	$199.52	7.826%	$215.1344	$215.13	$215.15	$215.10
Purchase #6	$135.65	12.433%	$152.5154	$152.52	$152.50	$152.50
Purchase #7	$89.65	13.335%	$101.6048	$101.60	$101.60	$101.60
7 purchase totals =	$912.19		$997.2160	$997.21	$997.15	$997.20