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	$241.87	3.580%	$250.5289	$250.53	$250.55	$250.50
Purchase #2	$71.38	9.289%	$78.0105	$78.01	$78.00	$78.00
Purchase #3	$37.85	6.554%	$40.3307	$40.33	$40.35	$40.30
Purchase #4	$235.35	7.497%	$252.9942	$252.99	$253.00	$253.00
Purchase #5	$215.73	6.729%	$230.2465	$230.25	$230.25	$230.20
Purchase #6	$116.51	9.737%	$127.8546	$127.85	$127.85	$127.90
Purchase #7	$111.88	6.377%	$119.0146	$119.01	$119.00	$119.00
7 purchase totals =	$1,030.57		$1,098.9800	$1,098.97	$1,099.00	$1,098.90