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	$184.40	13.299%	$208.9234	$208.92	$208.90	$208.90
Purchase #2	$44.93	9.410%	$49.1579	$49.16	$49.15	$49.20
Purchase #3	$52.29	13.397%	$59.2953	$59.30	$59.30	$59.30
Purchase #4	$212.90	3.144%	$219.5936	$219.59	$219.60	$219.60
Purchase #5	$170.96	5.797%	$180.8706	$180.87	$180.85	$180.90
Purchase #6	$185.41	3.645%	$192.1682	$192.17	$192.15	$192.20
Purchase #7	$101.28	4.247%	$105.5814	$105.58	$105.60	$105.60
7 purchase totals =	$952.17		$1,015.5904	$1,015.59	$1,015.55	$1,015.70