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	$54.43	8.413%	$59.0092	$59.01	$59.00	$59.00
Purchase #2	$22.42	6.285%	$23.8291	$23.83	$23.85	$23.80
Purchase #3	$101.71	5.388%	$107.1901	$107.19	$107.20	$107.20
Purchase #4	$66.50	3.549%	$68.8601	$68.86	$68.85	$68.90
Purchase #5	$155.90	7.483%	$167.566	$167.57	$167.55	$167.60
Purchase #6	$42.69	6.639%	$45.5242	$45.52	$45.50	$45.50
Purchase #7	$16.77	12.656%	$18.8924	$18.89	$18.90	$18.90
7 purchase totals =	$460.42		$490.8711	$490.87	$490.85	$490.90