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	$172.49	5.284%	$181.6044	$181.60	$181.60	$181.60
Purchase #2	$139.35	11.830%	$155.8351	$155.84	$155.85	$155.80
Purchase #3	$245.31	3.443%	$253.756	$253.76	$253.75	$253.80
Purchase #4	$17.73	10.527%	$19.5964	$19.60	$19.60	$19.60
Purchase #5	$145.69	12.659%	$164.1329	$164.13	$164.15	$164.10
Purchase #6	$123.50	6.493%	$131.5189	$131.52	$131.50	$131.50
Purchase #7	$117.36	5.379%	$123.6728	$123.67	$123.65	$123.70
7 purchase totals =	$961.43		$1,030.1165	$1,030.12	$1,030.10	$1,030.10