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	$113.88	11.582%	$127.0696	$127.07	$127.05	$127.10
Purchase #2	$91.72	11.602%	$102.3614	$102.36	$102.35	$102.40
Purchase #3	$70.72	9.712%	$77.5883	$77.59	$77.60	$77.60
Purchase #4	$242.93	6.447%	$258.5917	$258.59	$258.60	$258.60
Purchase #5	$206.65	4.362%	$215.6641	$215.66	$215.65	$215.70
Purchase #6	$151.28	11.405%	$168.5335	$168.53	$168.55	$168.50
Purchase #7	$26.40	12.136%	$29.6039	$29.60	$29.60	$29.60
7 purchase totals =	$903.58		$979.4125	$979.40	$979.40	$979.50