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	$136.82	13.201%	$154.8816	$154.88	$154.90	$154.90
Purchase #2	$158.37	5.168%	$166.5546	$166.55	$166.55	$166.60
Purchase #3	$211.87	6.593%	$225.8386	$225.84	$225.85	$225.80
Purchase #4	$164.31	6.426%	$174.8686	$174.87	$174.85	$174.90
Purchase #5	$119.82	6.457%	$127.5568	$127.56	$127.55	$127.60
Purchase #6	$169.60	10.535%	$187.4674	$187.47	$187.45	$187.50
Purchase #7	$220.58	7.506%	$237.1367	$237.14	$237.15	$237.10
7 purchase totals =	$1,181.37		$1,274.3043	$1,274.31	$1,274.30	$1,274.40