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	$158.68	7.183%	$170.078	$170.08	$170.10	$170.10
Purchase #2	$164.47	13.462%	$186.611	$186.61	$186.60	$186.60
Purchase #3	$31.81	3.230%	$32.8375	$32.84	$32.85	$32.80
Purchase #4	$39.64	10.644%	$43.8593	$43.86	$43.85	$43.90
Purchase #5	$101.82	4.616%	$106.52	$106.52	$106.50	$106.50
Purchase #6	$169.41	10.823%	$187.7452	$187.75	$187.75	$187.70
Purchase #7	$216.50	4.208%	$225.6103	$225.61	$225.60	$225.60
7 purchase totals =	$882.33		$953.2613	$953.27	$953.25	$953.20