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	$72.51	5.857%	$76.7569	$76.76	$76.75	$76.80
Purchase #2	$13.40	8.410%	$14.5269	$14.53	$14.55	$14.50
Purchase #3	$165.40	11.394%	$184.2457	$184.25	$184.25	$184.20
Purchase #4	$171.75	6.448%	$182.8244	$182.82	$182.80	$182.80
Purchase #5	$42.91	10.852%	$47.5666	$47.57	$47.55	$47.60
Purchase #6	$119.95	9.697%	$131.5816	$131.58	$131.60	$131.60
Purchase #7	$141.87	6.704%	$151.381	$151.38	$151.40	$151.40
7 purchase totals =	$727.79		$788.8831	$788.89	$788.90	$788.90