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	$99.37	12.664%	$111.9542	$111.95	$111.95	$112.00
Purchase #2	$42.70	11.629%	$47.6656	$47.67	$47.65	$47.70
Purchase #3	$190.87	7.738%	$205.6395	$205.64	$205.65	$205.60
Purchase #4	$110.25	5.169%	$115.9488	$115.95	$115.95	$115.90
Purchase #5	$247.71	5.257%	$260.7321	$260.73	$260.75	$260.70
Purchase #6	$126.89	11.727%	$141.7704	$141.77	$141.75	$141.80
Purchase #7	$99.66	11.533%	$111.1538	$111.15	$111.15	$111.20
7 purchase totals =	$917.45		$994.8644	$994.86	$994.85	$994.90