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	$209.61	6.600%	$223.4443	$223.44	$223.45	$223.40
Purchase #2	$249.29	4.506%	$260.523	$260.52	$260.50	$260.50
Purchase #3	$228.32	9.440%	$249.8734	$249.87	$249.85	$249.90
Purchase #4	$160.82	7.435%	$172.777	$172.78	$172.80	$172.80
Purchase #5	$240.72	8.128%	$260.2857	$260.29	$260.30	$260.30
Purchase #6	$47.26	8.357%	$51.2095	$51.21	$51.20	$51.20
Purchase #7	$190.59	11.111%	$211.7665	$211.77	$211.75	$211.80
7 purchase totals =	$1,326.61		$1,429.8794	$1,429.88	$1,429.85	$1,429.90