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	$105.51	8.381%	$114.3528	$114.35	$114.35	$114.40
Purchase #2	$205.61	11.187%	$228.6116	$228.61	$228.60	$228.60
Purchase #3	$79.88	12.797%	$90.1022	$90.10	$90.10	$90.10
Purchase #4	$159.51	13.798%	$181.5192	$181.52	$181.50	$181.50
Purchase #5	$50.71	5.206%	$53.35	$53.35	$53.35	$53.40
Purchase #6	$104.59	9.559%	$114.5878	$114.59	$114.60	$114.60
Purchase #7	$191.92	13.426%	$217.6872	$217.69	$217.70	$217.70
7 purchase totals =	$897.73		$1,000.2108	$1,000.21	$1,000.20	$1,000.30