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	$229.87	9.606%	$251.9513	$251.95	$251.95	$252.00
Purchase #2	$82.38	10.236%	$90.8124	$90.81	$90.80	$90.80
Purchase #3	$75.35	13.135%	$85.2472	$85.25	$85.25	$85.20
Purchase #4	$219.60	12.772%	$247.6473	$247.65	$247.65	$247.60
Purchase #5	$117.61	4.846%	$123.3094	$123.31	$123.30	$123.30
Purchase #6	$218.52	3.243%	$225.6066	$225.61	$225.60	$225.60
Purchase #7	$141.90	3.437%	$146.7771	$146.78	$146.80	$146.80
7 purchase totals =	$1,085.23		$1,171.3513	$1,171.36	$1,171.35	$1,171.30