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	$62.43	11.468%	$69.5895	$69.59	$69.60	$69.60
Purchase #2	$140.58	11.265%	$156.4163	$156.42	$156.40	$156.40
Purchase #3	$75.58	10.483%	$83.5031	$83.50	$83.50	$83.50
Purchase #4	$208.87	4.788%	$218.8707	$218.87	$218.85	$218.90
Purchase #5	$167.44	10.594%	$185.1786	$185.18	$185.20	$185.20
Purchase #6	$52.85	11.691%	$59.0287	$59.03	$59.05	$59.00
Purchase #7	$117.73	9.410%	$128.8084	$128.81	$128.80	$128.80
7 purchase totals =	$825.48		$901.3953	$901.40	$901.40	$901.40