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	$127.94	13.420%	$145.1095	$145.11	$145.10	$145.10
Purchase #2	$200.38	9.367%	$219.1496	$219.15	$219.15	$219.10
Purchase #3	$70.78	3.610%	$73.3352	$73.34	$73.35	$73.30
Purchase #4	$206.43	9.367%	$225.7663	$225.77	$225.75	$225.80
Purchase #5	$43.82	8.586%	$47.5824	$47.58	$47.60	$47.60
Purchase #6	$76.82	12.670%	$86.5531	$86.55	$86.55	$86.60
Purchase #7	$212.25	4.830%	$222.5017	$222.50	$222.50	$222.50
7 purchase totals =	$938.42		$1,019.9978	$1,020.00	$1,020.00	$1,020.00