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	$95.26	11.167%	$105.8977	$105.90	$105.90	$105.90
Purchase #2	$108.69	13.373%	$123.2251	$123.23	$123.25	$123.20
Purchase #3	$239.60	6.603%	$255.4208	$255.42	$255.40	$255.40
Purchase #4	$80.90	11.743%	$90.4001	$90.40	$90.40	$90.40
Purchase #5	$120.54	9.767%	$132.3131	$132.31	$132.30	$132.30
Purchase #6	$56.87	7.161%	$60.9425	$60.94	$60.95	$60.90
Purchase #7	$240.68	10.216%	$265.2679	$265.27	$265.25	$265.30
7 purchase totals =	$942.54		$1,033.4672	$1,033.47	$1,033.45	$1,033.40