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	$38.63	11.757%	$43.1717	$43.17	$43.15	$43.20
Purchase #2	$182.57	4.297%	$190.415	$190.42	$190.40	$190.40
Purchase #3	$192.84	11.545%	$215.1034	$215.10	$215.10	$215.10
Purchase #4	$64.54	3.204%	$66.6079	$66.61	$66.60	$66.60
Purchase #5	$234.83	4.398%	$245.1578	$245.16	$245.15	$245.20
Purchase #6	$24.36	11.731%	$27.2177	$27.22	$27.20	$27.20
Purchase #7	$237.59	3.376%	$245.611	$245.61	$245.60	$245.60
7 purchase totals =	$975.36		$1,033.2845	$1,033.29	$1,033.20	$1,033.30