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	$187.51	9.420%	$205.1734	$205.17	$205.15	$205.20
Purchase #2	$102.48	6.657%	$109.3021	$109.30	$109.30	$109.30
Purchase #3	$192.54	8.162%	$208.2551	$208.26	$208.25	$208.30
Purchase #4	$132.37	11.462%	$147.5422	$147.54	$147.55	$147.50
Purchase #5	$157.81	4.264%	$164.539	$164.54	$164.55	$164.50
Purchase #6	$234.84	6.708%	$250.5931	$250.59	$250.60	$250.60
Purchase #7	$175.49	5.488%	$185.1209	$185.12	$185.10	$185.10
7 purchase totals =	$1,183.04		$1,270.5258	$1,270.52	$1,270.50	$1,270.50