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	$93.28	13.227%	$105.6181	$105.62	$105.60	$105.60
Purchase #2	$108.34	13.374%	$122.8294	$122.83	$122.85	$122.80
Purchase #3	$182.55	5.369%	$192.3511	$192.35	$192.35	$192.40
Purchase #4	$131.43	12.677%	$148.0914	$148.09	$148.10	$148.10
Purchase #5	$79.29	12.670%	$89.336	$89.34	$89.35	$89.30
Purchase #6	$164.57	12.329%	$184.8598	$184.86	$184.85	$184.90
Purchase #7	$227.88	7.190%	$244.2646	$244.26	$244.25	$244.30
7 purchase totals =	$987.34		$1,087.3504	$1,087.35	$1,087.35	$1,087.40