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	$115.66	8.625%	$125.6357	$125.64	$125.65	$125.60
Purchase #2	$180.77	7.568%	$194.4507	$194.45	$194.45	$194.50
Purchase #3	$199.92	12.350%	$224.6101	$224.61	$224.60	$224.60
Purchase #4	$100.45	10.560%	$111.0575	$111.06	$111.05	$111.10
Purchase #5	$242.34	10.433%	$267.6233	$267.62	$267.60	$267.60
Purchase #6	$119.29	3.236%	$123.1502	$123.15	$123.15	$123.20
Purchase #7	$40.86	5.365%	$43.0521	$43.05	$43.05	$43.10
7 purchase totals =	$999.29		$1,089.5796	$1,089.58	$1,089.55	$1,089.70