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	$49.64	10.268%	$54.737	$54.74	$54.75	$54.70
Purchase #2	$181.57	9.213%	$198.298	$198.30	$198.30	$198.30
Purchase #3	$164.41	6.121%	$174.4735	$174.47	$174.45	$174.50
Purchase #4	$100.72	13.455%	$114.2719	$114.27	$114.25	$114.30
Purchase #5	$122.83	3.688%	$127.36	$127.36	$127.35	$127.40
Purchase #6	$99.93	11.549%	$111.4709	$111.47	$111.45	$111.50
Purchase #7	$200.83	12.190%	$225.3112	$225.31	$225.30	$225.30
7 purchase totals =	$919.93		$1,005.9225	$1,005.92	$1,005.85	$1,006.00