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	$151.25	6.224%	$160.6638	$160.66	$160.65	$160.70
Purchase #2	$59.72	5.105%	$62.7687	$62.77	$62.75	$62.80
Purchase #3	$137.67	13.867%	$156.7607	$156.76	$156.75	$156.80
Purchase #4	$160.87	3.658%	$166.7546	$166.75	$166.75	$166.80
Purchase #5	$111.94	6.417%	$119.1232	$119.12	$119.10	$119.10
Purchase #6	$110.83	7.763%	$119.4337	$119.43	$119.45	$119.40
Purchase #7	$104.29	4.776%	$109.2709	$109.27	$109.25	$109.30
7 purchase totals =	$836.57		$894.7756	$894.76	$894.70	$894.90