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	$49.58	7.174%	$53.1369	$53.14	$53.15	$53.10
Purchase #2	$148.33	9.870%	$162.9702	$162.97	$162.95	$163.00
Purchase #3	$241.45	8.558%	$262.1133	$262.11	$262.10	$262.10
Purchase #4	$41.59	9.368%	$45.4862	$45.49	$45.50	$45.50
Purchase #5	$135.61	4.335%	$141.4887	$141.49	$141.50	$141.50
Purchase #6	$192.28	12.274%	$215.8804	$215.88	$215.90	$215.90
Purchase #7	$216.39	10.229%	$238.5245	$238.52	$238.50	$238.50
7 purchase totals =	$1,025.23		$1,119.6002	$1,119.60	$1,119.60	$1,119.60