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	$86.35	3.595%	$89.4543	$89.45	$89.45	$89.50
Purchase #2	$55.48	5.397%	$58.4743	$58.47	$58.45	$58.50
Purchase #3	$106.52	7.712%	$114.7348	$114.73	$114.75	$114.70
Purchase #4	$199.86	3.691%	$207.2368	$207.24	$207.25	$207.20
Purchase #5	$165.29	4.139%	$172.1314	$172.13	$172.15	$172.10
Purchase #6	$104.72	9.215%	$114.3699	$114.37	$114.35	$114.40
Purchase #7	$68.28	3.646%	$70.7695	$70.77	$70.75	$70.80
7 purchase totals =	$786.50		$827.1710	$827.16	$827.15	$827.20