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	$172.61	7.332%	$185.2658	$185.27	$185.25	$185.30
Purchase #2	$71.77	13.615%	$81.5415	$81.54	$81.55	$81.50
Purchase #3	$211.54	10.416%	$233.574	$233.57	$233.55	$233.60
Purchase #4	$15.78	9.553%	$17.2875	$17.29	$17.30	$17.30
Purchase #5	$242.39	5.867%	$256.611	$256.61	$256.60	$256.60
Purchase #6	$130.40	4.470%	$136.2289	$136.23	$136.25	$136.20
Purchase #7	$166.77	6.376%	$177.4033	$177.40	$177.40	$177.40
7 purchase totals =	$1,011.26		$1,087.9120	$1,087.91	$1,087.90	$1,087.90