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	$228.86	11.368%	$254.8768	$254.88	$254.90	$254.90
Purchase #2	$231.81	7.493%	$249.1795	$249.18	$249.20	$249.20
Purchase #3	$80.95	10.590%	$89.5226	$89.52	$89.50	$89.50
Purchase #4	$66.86	8.107%	$72.2803	$72.28	$72.30	$72.30
Purchase #5	$98.75	8.746%	$107.3867	$107.39	$107.40	$107.40
Purchase #6	$127.25	3.475%	$131.6719	$131.67	$131.65	$131.70
Purchase #7	$121.49	7.127%	$130.1486	$130.15	$130.15	$130.10
7 purchase totals =	$955.97		$1,035.0664	$1,035.07	$1,035.10	$1,035.10