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	$57.30	3.709%	$59.4253	$59.43	$59.45	$59.40
Purchase #2	$146.88	10.447%	$162.2246	$162.22	$162.20	$162.20
Purchase #3	$213.37	5.621%	$225.3635	$225.36	$225.35	$225.40
Purchase #4	$183.88	12.773%	$207.367	$207.37	$207.35	$207.40
Purchase #5	$96.64	7.595%	$103.9798	$103.98	$104.00	$104.00
Purchase #6	$107.85	6.216%	$114.554	$114.55	$114.55	$114.60
Purchase #7	$90.53	12.130%	$101.5113	$101.51	$101.50	$101.50
7 purchase totals =	$896.45		$974.4255	$974.42	$974.40	$974.50