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	$97.68	7.500%	$105.006	$105.01	$105.00	$105.00
Purchase #2	$80.89	11.420%	$90.1276	$90.13	$90.15	$90.10
Purchase #3	$200.90	6.827%	$214.6154	$214.62	$214.60	$214.60
Purchase #4	$28.54	8.671%	$31.0147	$31.01	$31.00	$31.00
Purchase #5	$134.32	9.557%	$147.157	$147.16	$147.15	$147.20
Purchase #6	$32.42	9.778%	$35.59	$35.59	$35.60	$35.60
Purchase #7	$197.59	11.549%	$220.4097	$220.41	$220.40	$220.40
7 purchase totals =	$772.34		$843.9204	$843.93	$843.90	$843.90