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	$61.89	4.388%	$64.6057	$64.61	$64.60	$64.60
Purchase #2	$224.81	13.762%	$255.7484	$255.75	$255.75	$255.70
Purchase #3	$180.81	4.212%	$188.4257	$188.43	$188.45	$188.40
Purchase #4	$167.28	11.797%	$187.014	$187.01	$187.00	$187.00
Purchase #5	$216.98	3.565%	$224.7153	$224.72	$224.70	$224.70
Purchase #6	$92.96	13.565%	$105.57	$105.57	$105.55	$105.60
Purchase #7	$13.47	5.382%	$14.195	$14.20	$14.20	$14.20
7 purchase totals =	$958.20		$1,040.2741	$1,040.29	$1,040.25	$1,040.20