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	$182.71	7.483%	$196.3822	$196.38	$196.40	$196.40
Purchase #2	$13.60	10.244%	$14.9932	$14.99	$15.00	$15.00
Purchase #3	$180.42	11.179%	$200.5892	$200.59	$200.60	$200.60
Purchase #4	$100.49	12.599%	$113.1507	$113.15	$113.15	$113.20
Purchase #5	$193.33	10.431%	$213.4963	$213.50	$213.50	$213.50
Purchase #6	$34.39	3.409%	$35.5624	$35.56	$35.55	$35.60
Purchase #7	$171.80	9.810%	$188.6536	$188.65	$188.65	$188.70
7 purchase totals =	$876.74		$962.8276	$962.82	$962.85	$963.00