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	$131.63	9.528%	$144.1717	$144.17	$144.15	$144.20
Purchase #2	$177.40	12.507%	$199.5874	$199.59	$199.60	$199.60
Purchase #3	$134.29	3.376%	$138.8236	$138.82	$138.80	$138.80
Purchase #4	$96.30	10.495%	$106.4067	$106.41	$106.40	$106.40
Purchase #5	$91.81	11.534%	$102.3994	$102.40	$102.40	$102.40
Purchase #6	$186.56	5.301%	$196.4495	$196.45	$196.45	$196.40
Purchase #7	$233.87	9.400%	$255.8538	$255.85	$255.85	$255.90
7 purchase totals =	$1,051.86		$1,143.6921	$1,143.69	$1,143.65	$1,143.70