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	$215.40	12.297%	$241.8877	$241.89	$241.90	$241.90
Purchase #2	$156.55	10.687%	$173.2805	$173.28	$173.30	$173.30
Purchase #3	$79.53	4.200%	$82.8703	$82.87	$82.85	$82.90
Purchase #4	$250.42	13.577%	$284.4195	$284.42	$284.40	$284.40
Purchase #5	$42.60	4.604%	$44.5613	$44.56	$44.55	$44.60
Purchase #6	$200.31	13.213%	$226.777	$226.78	$226.80	$226.80
Purchase #7	$145.81	8.711%	$158.5115	$158.51	$158.50	$158.50
7 purchase totals =	$1,090.62		$1,212.3078	$1,212.31	$1,212.30	$1,212.40