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	$152.77	8.546%	$165.8257	$165.83	$165.85	$165.80
Purchase #2	$145.69	13.748%	$165.7195	$165.72	$165.70	$165.70
Purchase #3	$220.94	3.399%	$228.4498	$228.45	$228.45	$228.40
Purchase #4	$113.69	9.831%	$124.8669	$124.87	$124.85	$124.90
Purchase #5	$128.93	13.752%	$146.6605	$146.66	$146.65	$146.70
Purchase #6	$177.30	4.452%	$185.1934	$185.19	$185.20	$185.20
Purchase #7	$27.96	5.815%	$29.5859	$29.59	$29.60	$29.60
7 purchase totals =	$967.28		$1,046.3017	$1,046.31	$1,046.30	$1,046.30