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	$175.96	10.326%	$194.1296	$194.13	$194.15	$194.10
Purchase #2	$186.64	7.411%	$200.4719	$200.47	$200.45	$200.50
Purchase #3	$205.67	5.206%	$216.3772	$216.38	$216.40	$216.40
Purchase #4	$160.88	13.848%	$183.1587	$183.16	$183.15	$183.20
Purchase #5	$31.68	8.229%	$34.2869	$34.29	$34.30	$34.30
Purchase #6	$174.98	4.488%	$182.8331	$182.83	$182.85	$182.80
Purchase #7	$88.43	13.338%	$100.2248	$100.22	$100.20	$100.20
7 purchase totals =	$1,024.24		$1,111.4822	$1,111.48	$1,111.50	$1,111.50