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	$204.83	5.866%	$216.8453	$216.85	$216.85	$216.80
Purchase #2	$197.32	10.621%	$218.2774	$218.28	$218.30	$218.30
Purchase #3	$241.83	8.783%	$263.0699	$263.07	$263.05	$263.10
Purchase #4	$101.68	7.649%	$109.4575	$109.46	$109.45	$109.50
Purchase #5	$12.45	6.749%	$13.2903	$13.29	$13.30	$13.30
Purchase #6	$115.67	13.373%	$131.1385	$131.14	$131.15	$131.10
Purchase #7	$149.89	10.796%	$166.0721	$166.07	$166.05	$166.10
7 purchase totals =	$1,023.67		$1,118.1510	$1,118.16	$1,118.15	$1,118.20