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	$132.81	8.769%	$144.4561	$144.46	$144.45	$144.50
Purchase #2	$82.58	4.365%	$86.1846	$86.18	$86.20	$86.20
Purchase #3	$123.98	8.824%	$134.92	$134.92	$134.90	$134.90
Purchase #4	$60.39	6.508%	$64.3202	$64.32	$64.30	$64.30
Purchase #5	$144.38	10.329%	$159.293	$159.29	$159.30	$159.30
Purchase #6	$146.27	10.606%	$161.7834	$161.78	$161.80	$161.80
Purchase #7	$118.35	4.469%	$123.6391	$123.64	$123.65	$123.60
7 purchase totals =	$808.76		$874.5964	$874.59	$874.60	$874.60