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	$158.77	11.872%	$177.6192	$177.62	$177.60	$177.60
Purchase #2	$55.91	5.541%	$59.008	$59.01	$59.00	$59.00
Purchase #3	$234.70	7.307%	$251.8495	$251.85	$251.85	$251.80
Purchase #4	$145.85	13.479%	$165.5091	$165.51	$165.50	$165.50
Purchase #5	$109.53	12.839%	$123.5926	$123.59	$123.60	$123.60
Purchase #6	$126.52	10.107%	$139.3074	$139.31	$139.30	$139.30
Purchase #7	$15.41	12.821%	$17.3857	$17.39	$17.40	$17.40
7 purchase totals =	$846.69		$934.2715	$934.28	$934.25	$934.20