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	$196.78	6.737%	$210.0371	$210.04	$210.05	$210.00
Purchase #2	$20.82	12.816%	$23.4883	$23.49	$23.50	$23.50
Purchase #3	$27.60	12.777%	$31.1265	$31.13	$31.15	$31.10
Purchase #4	$169.83	9.187%	$185.4323	$185.43	$185.45	$185.40
Purchase #5	$140.61	5.605%	$148.4912	$148.49	$148.50	$148.50
Purchase #6	$162.92	11.267%	$181.2762	$181.28	$181.30	$181.30
Purchase #7	$48.60	10.699%	$53.7997	$53.80	$53.80	$53.80
7 purchase totals =	$767.16		$833.6513	$833.66	$833.75	$833.60