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	$128.55	9.312%	$140.5206	$140.52	$140.50	$140.50
Purchase #2	$37.78	7.537%	$40.6275	$40.63	$40.65	$40.60
Purchase #3	$143.71	13.283%	$162.799	$162.80	$162.80	$162.80
Purchase #4	$220.39	9.451%	$241.2191	$241.22	$241.20	$241.20
Purchase #5	$236.93	9.559%	$259.5781	$259.58	$259.60	$259.60
Purchase #6	$148.72	11.163%	$165.3216	$165.32	$165.30	$165.30
Purchase #7	$14.62	5.364%	$15.4042	$15.40	$15.40	$15.40
7 purchase totals =	$930.70		$1,025.4701	$1,025.47	$1,025.45	$1,025.40