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	$35.34	4.278%	$36.8518	$36.85	$36.85	$36.90
Purchase #2	$215.60	3.575%	$223.3077	$223.31	$223.30	$223.30
Purchase #3	$139.29	3.711%	$144.4591	$144.46	$144.45	$144.50
Purchase #4	$199.35	13.798%	$226.8563	$226.86	$226.85	$226.90
Purchase #5	$159.91	8.730%	$173.8701	$173.87	$173.85	$173.90
Purchase #6	$193.78	12.277%	$217.5704	$217.57	$217.55	$217.60
Purchase #7	$112.51	6.642%	$119.9829	$119.98	$120.00	$120.00
7 purchase totals =	$1,055.78		$1,142.8983	$1,142.90	$1,142.85	$1,143.10