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	$161.40	3.225%	$166.6052	$166.61	$166.60	$166.60
Purchase #2	$106.78	7.118%	$114.3806	$114.38	$114.40	$114.40
Purchase #3	$75.39	10.754%	$83.4974	$83.50	$83.50	$83.50
Purchase #4	$95.63	5.207%	$100.6095	$100.61	$100.60	$100.60
Purchase #5	$219.93	4.726%	$230.3239	$230.32	$230.30	$230.30
Purchase #6	$166.25	4.529%	$173.7795	$173.78	$173.80	$173.80
Purchase #7	$104.79	8.698%	$113.9046	$113.90	$113.90	$113.90
7 purchase totals =	$930.17		$983.1007	$983.10	$983.10	$983.10