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	$87.39	7.127%	$93.6183	$93.62	$93.60	$93.60
Purchase #2	$214.94	4.809%	$225.2765	$225.28	$225.30	$225.30
Purchase #3	$167.45	12.159%	$187.8102	$187.81	$187.80	$187.80
Purchase #4	$102.73	3.657%	$106.4868	$106.49	$106.50	$106.50
Purchase #5	$230.25	11.450%	$256.6136	$256.61	$256.60	$256.60
Purchase #6	$166.90	10.780%	$184.8918	$184.89	$184.90	$184.90
Purchase #7	$25.57	6.231%	$27.1633	$27.16	$27.15	$27.20
7 purchase totals =	$995.23		$1,081.8605	$1,081.86	$1,081.85	$1,081.90