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	$194.81	13.533%	$221.1736	$221.17	$221.15	$221.20
Purchase #2	$151.67	13.766%	$172.5489	$172.55	$172.55	$172.50
Purchase #3	$44.97	10.201%	$49.5574	$49.56	$49.55	$49.60
Purchase #4	$18.92	4.362%	$19.7453	$19.75	$19.75	$19.70
Purchase #5	$104.88	4.782%	$109.8954	$109.90	$109.90	$109.90
Purchase #6	$152.89	7.636%	$164.5647	$164.56	$164.55	$164.60
Purchase #7	$77.60	12.844%	$87.5669	$87.57	$87.55	$87.60
7 purchase totals =	$745.74		$825.0522	$825.06	$825.00	$825.10