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	$125.44	5.330%	$132.126	$132.13	$132.15	$132.10
Purchase #2	$166.27	12.223%	$186.5932	$186.59	$186.60	$186.60
Purchase #3	$147.90	4.420%	$154.4372	$154.44	$154.45	$154.40
Purchase #4	$155.72	7.221%	$166.9645	$166.96	$166.95	$167.00
Purchase #5	$157.79	10.569%	$174.4668	$174.47	$174.45	$174.50
Purchase #6	$69.52	12.615%	$78.2899	$78.29	$78.30	$78.30
Purchase #7	$132.34	13.556%	$150.28	$150.28	$150.30	$150.30
7 purchase totals =	$954.98		$1,043.1576	$1,043.16	$1,043.20	$1,043.20