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	$20.50	7.388%	$22.0145	$22.01	$22.00	$22.00
Purchase #2	$12.49	7.798%	$13.464	$13.46	$13.45	$13.50
Purchase #3	$25.48	12.198%	$28.5881	$28.59	$28.60	$28.60
Purchase #4	$75.27	13.549%	$85.4683	$85.47	$85.45	$85.50
Purchase #5	$169.56	12.228%	$190.2938	$190.29	$190.30	$190.30
Purchase #6	$155.53	4.622%	$162.7186	$162.72	$162.70	$162.70
Purchase #7	$65.56	10.744%	$72.6038	$72.60	$72.60	$72.60
7 purchase totals =	$524.39		$575.1511	$575.14	$575.10	$575.20