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	$98.42	5.531%	$103.8636	$103.86	$103.85	$103.90
Purchase #2	$131.48	4.247%	$137.064	$137.06	$137.05	$137.10
Purchase #3	$207.25	13.315%	$234.8453	$234.85	$234.85	$234.80
Purchase #4	$127.79	3.672%	$132.4824	$132.48	$132.50	$132.50
Purchase #5	$128.47	10.260%	$141.651	$141.65	$141.65	$141.70
Purchase #6	$25.99	9.390%	$28.4305	$28.43	$28.45	$28.40
Purchase #7	$99.51	8.628%	$108.0957	$108.10	$108.10	$108.10
7 purchase totals =	$818.91		$886.4325	$886.43	$886.45	$886.50