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	$9.39	9.364%	$10.2693	$10.27	$10.25	$10.30
Purchase #2	$64.99	11.712%	$72.6016	$72.60	$72.60	$72.60
Purchase #3	$223.34	13.784%	$254.1252	$254.13	$254.15	$254.10
Purchase #4	$237.45	3.799%	$246.4707	$246.47	$246.45	$246.50
Purchase #5	$248.93	13.156%	$281.6792	$281.68	$281.70	$281.70
Purchase #6	$56.54	4.586%	$59.1329	$59.13	$59.15	$59.10
Purchase #7	$126.30	6.283%	$134.2354	$134.24	$134.25	$134.20
7 purchase totals =	$966.94		$1,058.5143	$1,058.52	$1,058.55	$1,058.50