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	$65.49	10.631%	$72.4522	$72.45	$72.45	$72.50
Purchase #2	$155.76	9.586%	$170.6912	$170.69	$170.70	$170.70
Purchase #3	$160.35	3.730%	$166.3311	$166.33	$166.35	$166.30
Purchase #4	$103.38	11.304%	$115.0661	$115.07	$115.05	$115.10
Purchase #5	$233.77	10.825%	$259.0756	$259.08	$259.10	$259.10
Purchase #6	$173.60	11.320%	$193.2515	$193.25	$193.25	$193.30
Purchase #7	$119.33	3.119%	$123.0519	$123.05	$123.05	$123.10
7 purchase totals =	$1,011.68		$1,099.9196	$1,099.92	$1,099.95	$1,100.10