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	$42.27	5.683%	$44.6722	$44.67	$44.65	$44.70
Purchase #2	$211.91	5.744%	$224.0821	$224.08	$224.10	$224.10
Purchase #3	$163.60	9.754%	$179.5575	$179.56	$179.55	$179.60
Purchase #4	$186.86	5.190%	$196.558	$196.56	$196.55	$196.60
Purchase #5	$87.64	6.295%	$93.1569	$93.16	$93.15	$93.20
Purchase #6	$35.45	7.609%	$38.1474	$38.15	$38.15	$38.10
Purchase #7	$52.77	3.221%	$54.4697	$54.47	$54.45	$54.50
7 purchase totals =	$780.50		$830.6438	$830.65	$830.60	$830.80