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	$197.51	13.228%	$223.6366	$223.64	$223.65	$223.60
Purchase #2	$161.88	12.113%	$181.4885	$181.49	$181.50	$181.50
Purchase #3	$183.98	11.166%	$204.5232	$204.52	$204.50	$204.50
Purchase #4	$107.64	6.463%	$114.5968	$114.60	$114.60	$114.60
Purchase #5	$115.53	6.857%	$123.4519	$123.45	$123.45	$123.50
Purchase #6	$29.92	6.496%	$31.8636	$31.86	$31.85	$31.90
Purchase #7	$234.46	4.617%	$245.285	$245.29	$245.30	$245.30
7 purchase totals =	$1,030.92		$1,124.8456	$1,124.85	$1,124.85	$1,124.90