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	$47.27	7.545%	$50.8365	$50.84	$50.85	$50.80
Purchase #2	$17.61	7.582%	$18.9452	$18.95	$18.95	$18.90
Purchase #3	$159.68	3.697%	$165.5834	$165.58	$165.60	$165.60
Purchase #4	$185.94	5.733%	$196.5999	$196.60	$196.60	$196.60
Purchase #5	$31.75	6.388%	$33.7782	$33.78	$33.80	$33.80
Purchase #6	$106.97	10.367%	$118.0596	$118.06	$118.05	$118.10
Purchase #7	$91.39	12.678%	$102.9764	$102.98	$103.00	$103.00
7 purchase totals =	$640.61		$686.7792	$686.79	$686.85	$686.80