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	$159.59	8.766%	$173.5797	$173.58	$173.60	$173.60
Purchase #2	$204.29	7.146%	$218.8886	$218.89	$218.90	$218.90
Purchase #3	$146.89	6.746%	$156.7992	$156.80	$156.80	$156.80
Purchase #4	$86.44	4.346%	$90.1967	$90.20	$90.20	$90.20
Purchase #5	$103.29	6.444%	$109.946	$109.95	$109.95	$109.90
Purchase #6	$127.46	8.811%	$138.6905	$138.69	$138.70	$138.70
Purchase #7	$210.81	6.614%	$224.753	$224.75	$224.75	$224.80
7 purchase totals =	$1,038.77		$1,112.8537	$1,112.86	$1,112.90	$1,112.90