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	$222.96	7.735%	$240.206	$240.21	$240.20	$240.20
Purchase #2	$96.58	9.288%	$105.5504	$105.55	$105.55	$105.60
Purchase #3	$198.76	5.104%	$208.9047	$208.90	$208.90	$208.90
Purchase #4	$117.33	13.641%	$133.335	$133.34	$133.35	$133.30
Purchase #5	$158.82	10.510%	$175.512	$175.51	$175.50	$175.50
Purchase #6	$111.45	13.312%	$126.2862	$126.29	$126.30	$126.30
Purchase #7	$12.29	12.379%	$13.8114	$13.81	$13.80	$13.80
7 purchase totals =	$918.19		$1,003.6057	$1,003.61	$1,003.60	$1,003.60