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	$140.61	12.748%	$158.535	$158.54	$158.55	$158.50
Purchase #2	$160.60	3.246%	$165.8131	$165.81	$165.80	$165.80
Purchase #3	$62.72	8.189%	$67.8561	$67.86	$67.85	$67.90
Purchase #4	$81.84	12.597%	$92.1494	$92.15	$92.15	$92.10
Purchase #5	$108.30	5.804%	$114.5857	$114.59	$114.60	$114.60
Purchase #6	$221.91	6.409%	$236.1322	$236.13	$236.15	$236.10
Purchase #7	$174.95	13.253%	$198.1361	$198.14	$198.15	$198.10
7 purchase totals =	$950.93		$1,033.2076	$1,033.22	$1,033.25	$1,033.10