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	$183.81	11.143%	$204.2919	$204.29	$204.30	$204.30
Purchase #2	$223.61	10.181%	$246.3757	$246.38	$246.40	$246.40
Purchase #3	$56.54	8.651%	$61.4313	$61.43	$61.45	$61.40
Purchase #4	$216.90	7.491%	$233.148	$233.15	$233.15	$233.10
Purchase #5	$177.56	9.756%	$194.8828	$194.88	$194.90	$194.90
Purchase #6	$18.40	4.871%	$19.2963	$19.30	$19.30	$19.30
Purchase #7	$100.49	6.624%	$107.1465	$107.15	$107.15	$107.10
7 purchase totals =	$977.31		$1,066.5725	$1,066.58	$1,066.65	$1,066.50