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	$225.60	7.210%	$241.8658	$241.87	$241.85	$241.90
Purchase #2	$76.57	12.488%	$86.1321	$86.13	$86.15	$86.10
Purchase #3	$173.88	10.872%	$192.7842	$192.78	$192.80	$192.80
Purchase #4	$20.90	9.525%	$22.8907	$22.89	$22.90	$22.90
Purchase #5	$103.30	10.552%	$114.2002	$114.20	$114.20	$114.20
Purchase #6	$127.39	4.274%	$132.8346	$132.83	$132.85	$132.80
Purchase #7	$214.61	3.274%	$221.6363	$221.64	$221.65	$221.60
7 purchase totals =	$942.25		$1,012.3439	$1,012.34	$1,012.40	$1,012.30