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	$214.45	11.109%	$238.2733	$238.27	$238.25	$238.30
Purchase #2	$64.28	13.428%	$72.9115	$72.91	$72.90	$72.90
Purchase #3	$169.71	13.493%	$192.609	$192.61	$192.60	$192.60
Purchase #4	$143.34	11.341%	$159.5962	$159.60	$159.60	$159.60
Purchase #5	$118.58	8.591%	$128.7672	$128.77	$128.75	$128.80
Purchase #6	$232.25	12.546%	$261.3881	$261.39	$261.40	$261.40
Purchase #7	$174.30	7.740%	$187.7908	$187.79	$187.80	$187.80
7 purchase totals =	$1,116.91		$1,241.3361	$1,241.34	$1,241.30	$1,241.40