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	$218.64	13.518%	$248.1958	$248.20	$248.20	$248.20
Purchase #2	$202.68	5.397%	$213.6186	$213.62	$213.60	$213.60
Purchase #3	$234.69	5.502%	$247.6026	$247.60	$247.60	$247.60
Purchase #4	$53.63	6.598%	$57.1685	$57.17	$57.15	$57.20
Purchase #5	$155.28	3.317%	$160.4306	$160.43	$160.45	$160.40
Purchase #6	$105.83	5.233%	$111.3681	$111.37	$111.35	$111.40
Purchase #7	$88.82	4.643%	$92.9439	$92.94	$92.95	$92.90
7 purchase totals =	$1,059.57		$1,131.3281	$1,131.33	$1,131.30	$1,131.30