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	$184.95	10.456%	$204.2884	$204.29	$204.30	$204.30
Purchase #2	$202.44	10.168%	$223.0241	$223.02	$223.00	$223.00
Purchase #3	$144.82	5.194%	$152.342	$152.34	$152.35	$152.30
Purchase #4	$10.84	8.579%	$11.77	$11.77	$11.75	$11.80
Purchase #5	$146.97	3.264%	$151.7671	$151.77	$151.75	$151.80
Purchase #6	$152.75	8.688%	$166.0209	$166.02	$166.00	$166.00
Purchase #7	$86.25	5.251%	$90.779	$90.78	$90.80	$90.80
7 purchase totals =	$929.02		$999.9915	$999.99	$999.95	$1,000.00