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	$208.56	8.676%	$226.6547	$226.65	$226.65	$226.70
Purchase #2	$98.86	12.592%	$111.3085	$111.31	$111.30	$111.30
Purchase #3	$163.42	10.547%	$180.6559	$180.66	$180.65	$180.70
Purchase #4	$74.73	5.110%	$78.5487	$78.55	$78.55	$78.50
Purchase #5	$163.91	5.743%	$173.3234	$173.32	$173.30	$173.30
Purchase #6	$88.77	13.455%	$100.714	$100.71	$100.70	$100.70
Purchase #7	$9.90	11.610%	$11.0494	$11.05	$11.05	$11.00
7 purchase totals =	$808.15		$882.2546	$882.25	$882.20	$882.20