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	$51.32	10.162%	$56.5351	$56.54	$56.55	$56.50
Purchase #2	$205.64	11.591%	$229.4757	$229.48	$229.50	$229.50
Purchase #3	$144.72	8.199%	$156.5856	$156.59	$156.60	$156.60
Purchase #4	$199.55	4.706%	$208.9408	$208.94	$208.95	$208.90
Purchase #5	$58.62	6.388%	$62.3646	$62.36	$62.35	$62.40
Purchase #6	$134.30	10.719%	$148.6956	$148.70	$148.70	$148.70
Purchase #7	$171.66	10.850%	$190.2851	$190.29	$190.30	$190.30
7 purchase totals =	$965.81		$1,052.8825	$1,052.90	$1,052.95	$1,052.90