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	$245.84	12.674%	$276.9978	$277.00	$277.00	$277.00
Purchase #2	$118.28	4.385%	$123.4666	$123.47	$123.45	$123.50
Purchase #3	$149.70	12.733%	$168.7613	$168.76	$168.75	$168.80
Purchase #4	$127.81	9.476%	$139.9213	$139.92	$139.90	$139.90
Purchase #5	$87.39	3.431%	$90.3884	$90.39	$90.40	$90.40
Purchase #6	$164.53	12.107%	$184.4496	$184.45	$184.45	$184.40
Purchase #7	$55.85	8.230%	$60.4465	$60.45	$60.45	$60.40
7 purchase totals =	$949.40		$1,044.4315	$1,044.44	$1,044.40	$1,044.40