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	$160.27	10.656%	$177.3484	$177.35	$177.35	$177.30
Purchase #2	$166.45	11.447%	$185.5035	$185.50	$185.50	$185.50
Purchase #3	$114.39	7.660%	$123.1523	$123.15	$123.15	$123.20
Purchase #4	$134.35	13.629%	$152.6606	$152.66	$152.65	$152.70
Purchase #5	$100.27	9.252%	$109.547	$109.55	$109.55	$109.50
Purchase #6	$15.71	11.442%	$17.5075	$17.51	$17.50	$17.50
Purchase #7	$98.35	5.294%	$103.5566	$103.56	$103.55	$103.60
7 purchase totals =	$789.79		$869.2759	$869.28	$869.25	$869.30