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	$132.29	4.545%	$138.3026	$138.30	$138.30	$138.30
Purchase #2	$55.25	7.253%	$59.2573	$59.26	$59.25	$59.30
Purchase #3	$166.66	5.254%	$175.4163	$175.42	$175.40	$175.40
Purchase #4	$153.34	13.397%	$173.883	$173.88	$173.90	$173.90
Purchase #5	$168.63	13.780%	$191.8672	$191.87	$191.85	$191.90
Purchase #6	$187.45	9.447%	$205.1584	$205.16	$205.15	$205.20
Purchase #7	$213.61	11.725%	$238.6558	$238.66	$238.65	$238.70
7 purchase totals =	$1,077.23		$1,182.5406	$1,182.55	$1,182.50	$1,182.70