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	$250.83	13.717%	$285.2364	$285.24	$285.25	$285.20
Purchase #2	$233.87	9.773%	$256.7261	$256.73	$256.75	$256.70
Purchase #3	$68.64	5.862%	$72.6637	$72.66	$72.65	$72.70
Purchase #4	$87.39	9.387%	$95.5933	$95.59	$95.60	$95.60
Purchase #5	$115.85	12.834%	$130.7182	$130.72	$130.70	$130.70
Purchase #6	$81.46	9.472%	$89.1759	$89.18	$89.20	$89.20
Purchase #7	$161.27	12.482%	$181.3997	$181.40	$181.40	$181.40
7 purchase totals =	$999.31		$1,111.5133	$1,111.52	$1,111.55	$1,111.50