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	$102.91	8.691%	$111.8539	$111.85	$111.85	$111.90
Purchase #2	$161.28	3.707%	$167.2586	$167.26	$167.25	$167.30
Purchase #3	$184.36	13.283%	$208.8485	$208.85	$208.85	$208.80
Purchase #4	$49.72	9.569%	$54.4777	$54.48	$54.50	$54.50
Purchase #5	$6.25	9.233%	$6.8271	$6.83	$6.85	$6.80
Purchase #6	$156.80	6.702%	$167.3087	$167.31	$167.30	$167.30
Purchase #7	$7.96	8.204%	$8.613	$8.61	$8.60	$8.60
7 purchase totals =	$669.28		$725.1875	$725.19	$725.20	$725.20