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	$204.53	6.776%	$218.389	$218.39	$218.40	$218.40
Purchase #2	$153.79	3.487%	$159.1527	$159.15	$159.15	$159.20
Purchase #3	$164.32	10.234%	$181.1365	$181.14	$181.15	$181.10
Purchase #4	$69.60	12.606%	$78.3738	$78.37	$78.35	$78.40
Purchase #5	$108.51	10.225%	$119.6051	$119.61	$119.60	$119.60
Purchase #6	$118.52	12.317%	$133.1181	$133.12	$133.10	$133.10
Purchase #7	$150.81	3.264%	$155.7324	$155.73	$155.75	$155.70
7 purchase totals =	$970.08		$1,045.5076	$1,045.51	$1,045.50	$1,045.50