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	$166.60	10.704%	$184.4329	$184.43	$184.45	$184.40
Purchase #2	$155.91	12.788%	$175.8478	$175.85	$175.85	$175.80
Purchase #3	$147.43	12.690%	$166.1389	$166.14	$166.15	$166.10
Purchase #4	$83.42	8.583%	$90.5799	$90.58	$90.60	$90.60
Purchase #5	$170.83	7.163%	$183.0666	$183.07	$183.05	$183.10
Purchase #6	$186.89	7.276%	$200.4881	$200.49	$200.50	$200.50
Purchase #7	$147.51	8.594%	$160.187	$160.19	$160.20	$160.20
7 purchase totals =	$1,058.59		$1,160.7412	$1,160.75	$1,160.80	$1,160.70