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	$156.78	10.742%	$173.6213	$173.62	$173.60	$173.60
Purchase #2	$180.45	11.280%	$200.8048	$200.80	$200.80	$200.80
Purchase #3	$213.91	12.203%	$240.0134	$240.01	$240.00	$240.00
Purchase #4	$159.40	9.862%	$175.12	$175.12	$175.10	$175.10
Purchase #5	$14.35	9.256%	$15.6782	$15.68	$15.70	$15.70
Purchase #6	$35.60	4.797%	$37.3077	$37.31	$37.30	$37.30
Purchase #7	$102.76	8.571%	$111.5676	$111.57	$111.55	$111.60
7 purchase totals =	$863.25		$954.1130	$954.11	$954.05	$954.10