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	$134.29	3.754%	$139.3312	$139.33	$139.35	$139.30
Purchase #2	$224.28	10.694%	$248.2645	$248.26	$248.25	$248.30
Purchase #3	$234.42	9.396%	$256.4461	$256.45	$256.45	$256.40
Purchase #4	$138.30	8.106%	$149.5106	$149.51	$149.50	$149.50
Purchase #5	$105.29	10.646%	$116.4992	$116.50	$116.50	$116.50
Purchase #6	$139.88	7.354%	$150.1668	$150.17	$150.15	$150.20
Purchase #7	$205.64	4.576%	$215.0501	$215.05	$215.05	$215.10
7 purchase totals =	$1,182.10		$1,275.2685	$1,275.27	$1,275.25	$1,275.30