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	$165.98	6.144%	$176.1778	$176.18	$176.20	$176.20
Purchase #2	$207.81	7.702%	$223.8155	$223.82	$223.80	$223.80
Purchase #3	$119.77	9.651%	$131.329	$131.33	$131.35	$131.30
Purchase #4	$187.85	5.122%	$197.4717	$197.47	$197.45	$197.50
Purchase #5	$196.47	13.798%	$223.5789	$223.58	$223.60	$223.60
Purchase #6	$149.83	3.743%	$155.4381	$155.44	$155.45	$155.40
Purchase #7	$32.79	5.544%	$34.6079	$34.61	$34.60	$34.60
7 purchase totals =	$1,060.50		$1,142.4189	$1,142.43	$1,142.45	$1,142.40