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	$115.93	3.402%	$119.8739	$119.87	$119.85	$119.90
Purchase #2	$136.99	6.801%	$146.3067	$146.31	$146.30	$146.30
Purchase #3	$122.83	3.632%	$127.2912	$127.29	$127.30	$127.30
Purchase #4	$230.83	3.140%	$238.0781	$238.08	$238.10	$238.10
Purchase #5	$152.61	10.554%	$168.7165	$168.72	$168.70	$168.70
Purchase #6	$136.46	13.447%	$154.8098	$154.81	$154.80	$154.80
Purchase #7	$124.90	6.426%	$132.9261	$132.93	$132.95	$132.90
7 purchase totals =	$1,020.55		$1,088.0023	$1,088.01	$1,088.00	$1,088.00