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	$149.85	8.409%	$162.4509	$162.45	$162.45	$162.50
Purchase #2	$144.96	9.119%	$158.1789	$158.18	$158.20	$158.20
Purchase #3	$43.67	11.221%	$48.5702	$48.57	$48.55	$48.60
Purchase #4	$137.67	6.601%	$146.7576	$146.76	$146.75	$146.80
Purchase #5	$102.92	7.668%	$110.8119	$110.81	$110.80	$110.80
Purchase #6	$140.30	7.390%	$150.6682	$150.67	$150.65	$150.70
Purchase #7	$61.50	8.673%	$66.8339	$66.83	$66.85	$66.80
7 purchase totals =	$780.87		$844.2716	$844.27	$844.25	$844.40