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	$220.41	9.108%	$240.4849	$240.48	$240.50	$240.50
Purchase #2	$104.42	6.531%	$111.2397	$111.24	$111.25	$111.20
Purchase #3	$229.29	6.301%	$243.7376	$243.74	$243.75	$243.70
Purchase #4	$200.55	5.770%	$212.1217	$212.12	$212.10	$212.10
Purchase #5	$73.50	13.518%	$83.4357	$83.44	$83.45	$83.40
Purchase #6	$220.69	9.465%	$241.5783	$241.58	$241.60	$241.60
Purchase #7	$116.52	5.256%	$122.6443	$122.64	$122.65	$122.60
7 purchase totals =	$1,165.38		$1,255.2422	$1,255.24	$1,255.30	$1,255.10