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	$205.72	11.261%	$228.8861	$228.89	$228.90	$228.90
Purchase #2	$233.81	13.513%	$265.4047	$265.40	$265.40	$265.40
Purchase #3	$116.69	11.146%	$129.6963	$129.70	$129.70	$129.70
Purchase #4	$15.83	7.870%	$17.0758	$17.08	$17.10	$17.10
Purchase #5	$145.48	4.221%	$151.6207	$151.62	$151.60	$151.60
Purchase #6	$213.49	5.492%	$225.2149	$225.21	$225.20	$225.20
Purchase #7	$78.70	4.495%	$82.2376	$82.24	$82.25	$82.20
7 purchase totals =	$1,009.72		$1,100.1361	$1,100.14	$1,100.15	$1,100.10