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	$153.68	3.824%	$159.5567	$159.56	$159.55	$159.60
Purchase #2	$120.66	7.751%	$130.0124	$130.01	$130.00	$130.00
Purchase #3	$82.67	13.873%	$94.1388	$94.14	$94.15	$94.10
Purchase #4	$173.37	4.752%	$181.6085	$181.61	$181.60	$181.60
Purchase #5	$59.87	7.398%	$64.2992	$64.30	$64.30	$64.30
Purchase #6	$36.55	5.187%	$38.4458	$38.45	$38.45	$38.40
Purchase #7	$87.88	3.351%	$90.8249	$90.82	$90.80	$90.80
7 purchase totals =	$714.68		$758.8863	$758.89	$758.85	$758.80