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	$217.54	3.597%	$225.3649	$225.36	$225.35	$225.40
Purchase #2	$116.83	5.851%	$123.6657	$123.67	$123.65	$123.70
Purchase #3	$109.83	9.204%	$119.9388	$119.94	$119.95	$119.90
Purchase #4	$178.28	5.183%	$187.5203	$187.52	$187.50	$187.50
Purchase #5	$143.30	4.593%	$149.8818	$149.88	$149.90	$149.90
Purchase #6	$132.96	9.227%	$145.2282	$145.23	$145.25	$145.20
Purchase #7	$56.52	10.540%	$62.4772	$62.48	$62.50	$62.50
7 purchase totals =	$955.26		$1,014.0769	$1,014.08	$1,014.10	$1,014.10