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	$147.94	9.433%	$161.8952	$161.90	$161.90	$161.90
Purchase #2	$13.71	9.272%	$14.9812	$14.98	$15.00	$15.00
Purchase #3	$101.75	5.577%	$107.4246	$107.42	$107.40	$107.40
Purchase #4	$77.88	13.274%	$88.2178	$88.22	$88.20	$88.20
Purchase #5	$110.78	12.682%	$124.8291	$124.83	$124.85	$124.80
Purchase #6	$107.72	10.855%	$119.413	$119.41	$119.40	$119.40
Purchase #7	$100.55	10.536%	$111.1439	$111.14	$111.15	$111.10
7 purchase totals =	$660.33		$727.9048	$727.90	$727.90	$727.80