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	$176.28	8.680%	$191.5811	$191.58	$191.60	$191.60
Purchase #2	$106.32	4.191%	$110.7759	$110.78	$110.80	$110.80
Purchase #3	$75.45	9.628%	$82.7143	$82.71	$82.70	$82.70
Purchase #4	$56.90	7.412%	$61.1174	$61.12	$61.10	$61.10
Purchase #5	$133.83	4.232%	$139.4937	$139.49	$139.50	$139.50
Purchase #6	$161.42	3.116%	$166.4498	$166.45	$166.45	$166.40
Purchase #7	$107.31	5.115%	$112.7989	$112.80	$112.80	$112.80
7 purchase totals =	$817.51		$864.9311	$864.93	$864.95	$864.90