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	$147.54	11.576%	$164.6192	$164.62	$164.60	$164.60
Purchase #2	$38.47	13.819%	$43.7862	$43.79	$43.80	$43.80
Purchase #3	$165.87	4.447%	$173.2462	$173.25	$173.25	$173.20
Purchase #4	$171.90	11.379%	$191.4605	$191.46	$191.45	$191.50
Purchase #5	$132.35	11.460%	$147.5173	$147.52	$147.50	$147.50
Purchase #6	$235.91	3.543%	$244.2683	$244.27	$244.25	$244.30
Purchase #7	$246.65	13.377%	$279.6444	$279.64	$279.65	$279.60
7 purchase totals =	$1,138.69		$1,244.5421	$1,244.55	$1,244.50	$1,244.50