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	$57.39	7.804%	$61.8687	$61.87	$61.85	$61.90
Purchase #2	$247.58	13.242%	$280.3645	$280.36	$280.35	$280.40
Purchase #3	$118.66	8.132%	$128.3094	$128.31	$128.30	$128.30
Purchase #4	$24.87	3.854%	$25.8285	$25.83	$25.85	$25.80
Purchase #5	$5.74	8.290%	$6.2158	$6.22	$6.20	$6.20
Purchase #6	$127.87	5.267%	$134.6049	$134.60	$134.60	$134.60
Purchase #7	$92.83	11.208%	$103.2344	$103.23	$103.25	$103.20
7 purchase totals =	$674.94		$740.4262	$740.42	$740.40	$740.40