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	$139.28	10.160%	$153.4308	$153.43	$153.45	$153.40
Purchase #2	$15.53	10.127%	$17.1027	$17.10	$17.10	$17.10
Purchase #3	$112.32	13.674%	$127.6786	$127.68	$127.70	$127.70
Purchase #4	$237.66	11.254%	$264.4063	$264.41	$264.40	$264.40
Purchase #5	$231.97	13.503%	$263.2929	$263.29	$263.30	$263.30
Purchase #6	$114.29	11.521%	$127.4574	$127.46	$127.45	$127.50
Purchase #7	$18.88	13.260%	$21.3835	$21.38	$21.40	$21.40
7 purchase totals =	$869.93		$974.7522	$974.75	$974.80	$974.80