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	$237.97	7.864%	$256.684	$256.68	$256.70	$256.70
Purchase #2	$96.97	9.654%	$106.3315	$106.33	$106.35	$106.30
Purchase #3	$87.51	3.369%	$90.4582	$90.46	$90.45	$90.50
Purchase #4	$17.76	5.730%	$18.7776	$18.78	$18.80	$18.80
Purchase #5	$32.81	13.553%	$37.2567	$37.26	$37.25	$37.30
Purchase #6	$52.39	9.784%	$57.5158	$57.52	$57.50	$57.50
Purchase #7	$112.31	8.126%	$121.4363	$121.44	$121.45	$121.40
7 purchase totals =	$637.72		$688.4601	$688.47	$688.50	$688.50