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	$151.78	4.655%	$158.8454	$158.85	$158.85	$158.80
Purchase #2	$59.33	3.694%	$61.5217	$61.52	$61.50	$61.50
Purchase #3	$169.86	12.349%	$190.836	$190.84	$190.85	$190.80
Purchase #4	$228.79	7.854%	$246.7592	$246.76	$246.75	$246.80
Purchase #5	$62.38	12.740%	$70.3272	$70.33	$70.35	$70.30
Purchase #6	$190.60	5.715%	$201.4928	$201.49	$201.50	$201.50
Purchase #7	$42.92	6.732%	$45.8094	$45.81	$45.80	$45.80
7 purchase totals =	$905.66		$975.5917	$975.60	$975.60	$975.50