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	$74.92	11.308%	$83.392	$83.39	$83.40	$83.40
Purchase #2	$127.85	12.689%	$144.0729	$144.07	$144.05	$144.10
Purchase #3	$249.35	5.341%	$262.6678	$262.67	$262.65	$262.70
Purchase #4	$92.36	7.246%	$99.0524	$99.05	$99.05	$99.10
Purchase #5	$35.40	11.857%	$39.5974	$39.60	$39.60	$39.60
Purchase #6	$178.99	3.297%	$184.8913	$184.89	$184.90	$184.90
Purchase #7	$214.27	11.666%	$239.2667	$239.27	$239.25	$239.30
7 purchase totals =	$973.14		$1,052.9405	$1,052.94	$1,052.90	$1,053.10