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	$85.39	4.420%	$89.1642	$89.16	$89.15	$89.20
Purchase #2	$116.30	5.500%	$122.6965	$122.70	$122.70	$122.70
Purchase #3	$103.51	9.456%	$113.2979	$113.30	$113.30	$113.30
Purchase #4	$212.92	3.582%	$220.5468	$220.55	$220.55	$220.50
Purchase #5	$250.71	4.745%	$262.6062	$262.61	$262.60	$262.60
Purchase #6	$64.77	10.104%	$71.3144	$71.31	$71.30	$71.30
Purchase #7	$128.32	3.328%	$132.5905	$132.59	$132.60	$132.60
7 purchase totals =	$961.92		$1,012.2165	$1,012.22	$1,012.20	$1,012.20