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	$95.55	10.836%	$105.9038	$105.90	$105.90	$105.90
Purchase #2	$87.77	10.682%	$97.1456	$97.15	$97.15	$97.10
Purchase #3	$6.72	13.172%	$7.6052	$7.61	$7.60	$7.60
Purchase #4	$118.50	10.159%	$130.5384	$130.54	$130.55	$130.50
Purchase #5	$139.65	12.249%	$156.7557	$156.76	$156.75	$156.80
Purchase #6	$152.99	4.767%	$160.283	$160.28	$160.30	$160.30
Purchase #7	$78.76	10.270%	$86.8487	$86.85	$86.85	$86.80
7 purchase totals =	$679.94		$745.0804	$745.09	$745.10	$745.00