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	$66.68	9.782%	$73.2026	$73.20	$73.20	$73.20
Purchase #2	$172.77	7.165%	$185.149	$185.15	$185.15	$185.10
Purchase #3	$18.89	3.715%	$19.5918	$19.59	$19.60	$19.60
Purchase #4	$106.74	4.726%	$111.7845	$111.78	$111.80	$111.80
Purchase #5	$100.96	13.528%	$114.6179	$114.62	$114.60	$114.60
Purchase #6	$150.46	11.321%	$167.4936	$167.49	$167.50	$167.50
Purchase #7	$71.58	3.237%	$73.897	$73.90	$73.90	$73.90
7 purchase totals =	$688.08		$745.7364	$745.73	$745.75	$745.70