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	$153.31	9.800%	$168.3344	$168.33	$168.35	$168.30
Purchase #2	$224.90	7.869%	$242.5974	$242.60	$242.60	$242.60
Purchase #3	$50.59	6.853%	$54.0569	$54.06	$54.05	$54.10
Purchase #4	$176.94	11.443%	$197.1872	$197.19	$197.20	$197.20
Purchase #5	$104.50	7.667%	$112.512	$112.51	$112.50	$112.50
Purchase #6	$49.47	11.768%	$55.2916	$55.29	$55.30	$55.30
Purchase #7	$122.98	7.431%	$132.1186	$132.12	$132.10	$132.10
7 purchase totals =	$882.69		$962.0981	$962.10	$962.10	$962.10