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	$94.49	3.265%	$97.5751	$97.58	$97.60	$97.60
Purchase #2	$216.45	6.298%	$230.082	$230.08	$230.10	$230.10
Purchase #3	$196.93	9.494%	$215.6265	$215.63	$215.65	$215.60
Purchase #4	$247.88	13.583%	$281.5495	$281.55	$281.55	$281.50
Purchase #5	$82.60	8.414%	$89.55	$89.55	$89.55	$89.60
Purchase #6	$73.52	5.256%	$77.3842	$77.38	$77.40	$77.40
Purchase #7	$209.85	4.136%	$218.5294	$218.53	$218.55	$218.50
7 purchase totals =	$1,121.72		$1,210.2967	$1,210.30	$1,210.40	$1,210.30