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	$146.39	13.758%	$166.5303	$166.53	$166.55	$166.50
Purchase #2	$176.48	9.316%	$192.9209	$192.92	$192.90	$192.90
Purchase #3	$173.45	4.597%	$181.4235	$181.42	$181.40	$181.40
Purchase #4	$147.94	12.606%	$166.5893	$166.59	$166.60	$166.60
Purchase #5	$72.43	7.357%	$77.7587	$77.76	$77.75	$77.80
Purchase #6	$50.26	5.246%	$52.8966	$52.90	$52.90	$52.90
Purchase #7	$190.28	12.112%	$213.3267	$213.33	$213.35	$213.30
7 purchase totals =	$957.23		$1,051.4460	$1,051.45	$1,051.45	$1,051.40