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	$166.28	9.853%	$182.6636	$182.66	$182.65	$182.70
Purchase #2	$66.26	9.337%	$72.4467	$72.45	$72.45	$72.40
Purchase #3	$33.26	11.213%	$36.9894	$36.99	$37.00	$37.00
Purchase #4	$181.78	5.396%	$191.5888	$191.59	$191.60	$191.60
Purchase #5	$92.99	11.428%	$103.6169	$103.62	$103.60	$103.60
Purchase #6	$201.31	13.382%	$228.2493	$228.25	$228.25	$228.20
Purchase #7	$121.40	4.696%	$127.1009	$127.10	$127.10	$127.10
7 purchase totals =	$863.28		$942.6556	$942.66	$942.65	$942.60