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	$170.59	13.831%	$194.1843	$194.18	$194.20	$194.20
Purchase #2	$12.26	10.284%	$13.5208	$13.52	$13.50	$13.50
Purchase #3	$142.62	9.857%	$156.6781	$156.68	$156.70	$156.70
Purchase #4	$38.44	8.781%	$41.8154	$41.82	$41.80	$41.80
Purchase #5	$65.50	11.715%	$73.1733	$73.17	$73.15	$73.20
Purchase #6	$139.90	3.315%	$144.5377	$144.54	$144.55	$144.50
Purchase #7	$97.76	13.819%	$111.2695	$111.27	$111.25	$111.30
7 purchase totals =	$667.07		$735.1791	$735.18	$735.15	$735.20