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	$235.91	11.525%	$263.0986	$263.10	$263.10	$263.10
Purchase #2	$167.99	3.204%	$173.3724	$173.37	$173.35	$173.40
Purchase #3	$133.72	10.186%	$147.3407	$147.34	$147.35	$147.30
Purchase #4	$40.94	11.118%	$45.4917	$45.49	$45.50	$45.50
Purchase #5	$229.59	11.754%	$256.576	$256.58	$256.60	$256.60
Purchase #6	$6.55	10.546%	$7.2408	$7.24	$7.25	$7.20
Purchase #7	$99.33	12.620%	$111.8654	$111.87	$111.85	$111.90
7 purchase totals =	$914.03		$1,004.9856	$1,004.99	$1,005.00	$1,005.00