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	$112.66	13.531%	$127.904	$127.90	$127.90	$127.90
Purchase #2	$57.94	9.794%	$63.6146	$63.61	$63.60	$63.60
Purchase #3	$31.30	12.695%	$35.2735	$35.27	$35.25	$35.30
Purchase #4	$188.44	10.511%	$208.2469	$208.25	$208.25	$208.20
Purchase #5	$48.46	8.637%	$52.6455	$52.65	$52.65	$52.60
Purchase #6	$105.63	3.602%	$109.4348	$109.43	$109.45	$109.40
Purchase #7	$33.32	3.528%	$34.4955	$34.50	$34.50	$34.50
7 purchase totals =	$577.75		$631.6148	$631.61	$631.60	$631.50