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	$99.68	10.215%	$109.8623	$109.86	$109.85	$109.90
Purchase #2	$85.50	13.587%	$97.1169	$97.12	$97.10	$97.10
Purchase #3	$12.96	13.443%	$14.7022	$14.70	$14.70	$14.70
Purchase #4	$148.72	8.161%	$160.857	$160.86	$160.85	$160.90
Purchase #5	$131.52	3.783%	$136.4954	$136.50	$136.50	$136.50
Purchase #6	$84.93	3.394%	$87.8125	$87.81	$87.80	$87.80
Purchase #7	$143.61	5.822%	$151.971	$151.97	$151.95	$152.00
7 purchase totals =	$706.92		$758.8173	$758.82	$758.75	$758.90