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	$50.75	5.147%	$53.3621	$53.36	$53.35	$53.40
Purchase #2	$180.76	13.481%	$205.1283	$205.13	$205.15	$205.10
Purchase #3	$125.39	10.626%	$138.7139	$138.71	$138.70	$138.70
Purchase #4	$131.89	6.191%	$140.0553	$140.06	$140.05	$140.10
Purchase #5	$225.45	5.505%	$237.861	$237.86	$237.85	$237.90
Purchase #6	$121.92	4.619%	$127.5515	$127.55	$127.55	$127.60
Purchase #7	$153.38	3.739%	$159.1149	$159.11	$159.10	$159.10
7 purchase totals =	$989.54		$1,061.7870	$1,061.78	$1,061.75	$1,061.90