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	$138.53	10.838%	$153.5439	$153.54	$153.55	$153.50
Purchase #2	$33.46	3.840%	$34.7449	$34.74	$34.75	$34.70
Purchase #3	$121.74	4.774%	$127.5519	$127.55	$127.55	$127.60
Purchase #4	$61.61	7.225%	$66.0613	$66.06	$66.05	$66.10
Purchase #5	$71.72	9.168%	$78.2953	$78.30	$78.30	$78.30
Purchase #6	$127.95	5.112%	$134.4908	$134.49	$134.50	$134.50
Purchase #7	$242.85	11.413%	$270.5665	$270.57	$270.55	$270.60
7 purchase totals =	$797.86		$865.2546	$865.25	$865.25	$865.30