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	$127.65	4.669%	$133.61	$133.61	$133.60	$133.60
Purchase #2	$173.68	9.445%	$190.0841	$190.08	$190.10	$190.10
Purchase #3	$192.88	8.621%	$209.5082	$209.51	$209.50	$209.50
Purchase #4	$35.28	9.531%	$38.6425	$38.64	$38.65	$38.60
Purchase #5	$146.61	7.383%	$157.4342	$157.43	$157.45	$157.40
Purchase #6	$35.71	5.258%	$37.5876	$37.59	$37.60	$37.60
Purchase #7	$228.64	4.218%	$238.284	$238.28	$238.30	$238.30
7 purchase totals =	$940.45		$1,005.1506	$1,005.14	$1,005.20	$1,005.10