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	$103.77	10.121%	$114.2726	$114.27	$114.25	$114.30
Purchase #2	$81.78	10.271%	$90.1796	$90.18	$90.20	$90.20
Purchase #3	$130.34	12.810%	$147.0366	$147.04	$147.05	$147.00
Purchase #4	$51.53	12.212%	$57.8228	$57.82	$57.80	$57.80
Purchase #5	$10.40	11.195%	$11.5643	$11.56	$11.55	$11.60
Purchase #6	$118.69	6.539%	$126.4511	$126.45	$126.45	$126.50
Purchase #7	$212.94	13.382%	$241.4356	$241.44	$241.45	$241.40
7 purchase totals =	$709.45		$788.7626	$788.76	$788.75	$788.80