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	$179.50	3.313%	$185.4468	$185.45	$185.45	$185.40
Purchase #2	$184.45	12.277%	$207.0949	$207.09	$207.10	$207.10
Purchase #3	$229.61	3.327%	$237.2491	$237.25	$237.25	$237.20
Purchase #4	$70.99	11.146%	$78.9025	$78.90	$78.90	$78.90
Purchase #5	$13.56	9.602%	$14.862	$14.86	$14.85	$14.90
Purchase #6	$122.29	4.105%	$127.31	$127.31	$127.30	$127.30
Purchase #7	$30.72	13.818%	$34.9649	$34.96	$34.95	$35.00
7 purchase totals =	$831.12		$885.8302	$885.82	$885.80	$885.80