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	$135.98	3.712%	$141.0276	$141.03	$141.05	$141.00
Purchase #2	$198.40	3.523%	$205.3896	$205.39	$205.40	$205.40
Purchase #3	$239.34	11.397%	$266.6176	$266.62	$266.60	$266.60
Purchase #4	$71.51	10.142%	$78.7625	$78.76	$78.75	$78.80
Purchase #5	$35.34	9.848%	$38.8203	$38.82	$38.80	$38.80
Purchase #6	$86.39	7.167%	$92.5816	$92.58	$92.60	$92.60
Purchase #7	$237.55	7.544%	$255.4708	$255.47	$255.45	$255.50
7 purchase totals =	$1,004.51		$1,078.6700	$1,078.67	$1,078.65	$1,078.70