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	$210.88	11.138%	$234.3678	$234.37	$234.35	$234.40
Purchase #2	$61.93	8.287%	$67.0621	$67.06	$67.05	$67.10
Purchase #3	$151.96	4.526%	$158.8377	$158.84	$158.85	$158.80
Purchase #4	$159.94	12.403%	$179.7774	$179.78	$179.80	$179.80
Purchase #5	$155.76	3.656%	$161.4546	$161.45	$161.45	$161.50
Purchase #6	$60.30	12.113%	$67.6041	$67.60	$67.60	$67.60
Purchase #7	$155.73	8.682%	$169.2505	$169.25	$169.25	$169.30
7 purchase totals =	$956.50		$1,038.3542	$1,038.35	$1,038.35	$1,038.50