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	$102.31	13.521%	$116.1433	$116.14	$116.15	$116.10
Purchase #2	$167.32	11.858%	$187.1608	$187.16	$187.15	$187.20
Purchase #3	$217.39	12.351%	$244.2398	$244.24	$244.25	$244.20
Purchase #4	$250.39	6.341%	$266.2672	$266.27	$266.25	$266.30
Purchase #5	$87.51	9.725%	$96.0203	$96.02	$96.00	$96.00
Purchase #6	$56.60	4.812%	$59.3236	$59.32	$59.30	$59.30
Purchase #7	$208.30	5.162%	$219.0524	$219.05	$219.05	$219.10
7 purchase totals =	$1,089.82		$1,188.2074	$1,188.20	$1,188.15	$1,188.20