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	$150.65	7.180%	$161.4667	$161.47	$161.45	$161.50
Purchase #2	$139.64	8.568%	$151.6044	$151.60	$151.60	$151.60
Purchase #3	$122.59	12.436%	$137.8353	$137.84	$137.85	$137.80
Purchase #4	$85.46	10.738%	$94.6367	$94.64	$94.65	$94.60
Purchase #5	$192.88	13.278%	$218.4906	$218.49	$218.50	$218.50
Purchase #6	$121.93	7.416%	$130.9723	$130.97	$130.95	$131.00
Purchase #7	$154.54	7.760%	$166.5323	$166.53	$166.55	$166.50
7 purchase totals =	$967.69		$1,061.5383	$1,061.54	$1,061.55	$1,061.50