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	$105.55	5.709%	$111.5758	$111.58	$111.60	$111.60
Purchase #2	$41.78	3.583%	$43.277	$43.28	$43.30	$43.30
Purchase #3	$90.99	13.114%	$102.9224	$102.92	$102.90	$102.90
Purchase #4	$201.75	9.807%	$221.5356	$221.54	$221.55	$221.50
Purchase #5	$26.92	4.221%	$28.0563	$28.06	$28.05	$28.10
Purchase #6	$60.71	4.352%	$63.3521	$63.35	$63.35	$63.40
Purchase #7	$19.59	11.117%	$21.7678	$21.77	$21.75	$21.80
7 purchase totals =	$547.29		$592.4870	$592.50	$592.50	$592.60