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	$108.68	8.397%	$117.8059	$117.81	$117.80	$117.80
Purchase #2	$232.52	11.318%	$258.8366	$258.84	$258.85	$258.80
Purchase #3	$148.43	3.396%	$153.4707	$153.47	$153.45	$153.50
Purchase #4	$169.58	12.215%	$190.2942	$190.29	$190.30	$190.30
Purchase #5	$98.94	9.196%	$108.0385	$108.04	$108.05	$108.00
Purchase #6	$61.53	6.494%	$65.5258	$65.53	$65.55	$65.50
Purchase #7	$118.27	4.240%	$123.2846	$123.28	$123.30	$123.30
7 purchase totals =	$937.95		$1,017.2563	$1,017.26	$1,017.30	$1,017.20