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	$223.94	4.182%	$233.3052	$233.31	$233.30	$233.30
Purchase #2	$164.51	8.527%	$178.5378	$178.54	$178.55	$178.50
Purchase #3	$167.45	8.301%	$181.35	$181.35	$181.35	$181.40
Purchase #4	$242.27	3.478%	$250.6962	$250.70	$250.70	$250.70
Purchase #5	$152.28	4.348%	$158.9011	$158.90	$158.90	$158.90
Purchase #6	$151.51	12.212%	$170.0124	$170.01	$170.00	$170.00
Purchase #7	$89.61	11.795%	$100.1795	$100.18	$100.20	$100.20
7 purchase totals =	$1,191.57		$1,272.9822	$1,272.99	$1,273.00	$1,273.00