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	$73.36	12.117%	$82.249	$82.25	$82.25	$82.20
Purchase #2	$175.29	8.464%	$190.1265	$190.13	$190.15	$190.10
Purchase #3	$98.72	10.577%	$109.1616	$109.16	$109.15	$109.20
Purchase #4	$216.28	4.336%	$225.6579	$225.66	$225.65	$225.70
Purchase #5	$127.37	13.288%	$144.2949	$144.29	$144.30	$144.30
Purchase #6	$172.63	9.840%	$189.6168	$189.62	$189.60	$189.60
Purchase #7	$123.30	10.599%	$136.3686	$136.37	$136.35	$136.40
7 purchase totals =	$986.95		$1,077.4753	$1,077.48	$1,077.45	$1,077.50