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	$223.45	13.864%	$254.4291	$254.43	$254.45	$254.40
Purchase #2	$229.86	11.345%	$255.9376	$255.94	$255.95	$255.90
Purchase #3	$25.62	5.855%	$27.1201	$27.12	$27.10	$27.10
Purchase #4	$66.82	8.395%	$72.4295	$72.43	$72.45	$72.40
Purchase #5	$112.46	3.322%	$116.1959	$116.20	$116.20	$116.20
Purchase #6	$106.79	7.480%	$114.7779	$114.78	$114.80	$114.80
Purchase #7	$195.58	9.250%	$213.6712	$213.67	$213.65	$213.70
7 purchase totals =	$960.58		$1,054.5613	$1,054.57	$1,054.60	$1,054.50