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	$205.61	12.378%	$231.0604	$231.06	$231.05	$231.10
Purchase #2	$179.55	3.397%	$185.6493	$185.65	$185.65	$185.60
Purchase #3	$229.38	5.631%	$242.2964	$242.30	$242.30	$242.30
Purchase #4	$63.28	8.231%	$68.4886	$68.49	$68.50	$68.50
Purchase #5	$76.49	7.794%	$82.4516	$82.45	$82.45	$82.50
Purchase #6	$29.66	13.149%	$33.56	$33.56	$33.55	$33.60
Purchase #7	$16.53	12.574%	$18.6085	$18.61	$18.60	$18.60
7 purchase totals =	$800.50		$862.1148	$862.12	$862.10	$862.20