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	$210.83	13.626%	$239.5577	$239.56	$239.55	$239.60
Purchase #2	$225.92	7.685%	$243.282	$243.28	$243.30	$243.30
Purchase #3	$208.29	11.310%	$231.8476	$231.85	$231.85	$231.80
Purchase #4	$13.59	3.312%	$14.0401	$14.04	$14.05	$14.00
Purchase #5	$11.32	13.566%	$12.8557	$12.86	$12.85	$12.90
Purchase #6	$169.61	6.315%	$180.3209	$180.32	$180.30	$180.30
Purchase #7	$112.30	13.397%	$127.3448	$127.34	$127.35	$127.30
7 purchase totals =	$951.86		$1,049.2488	$1,049.25	$1,049.25	$1,049.20