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	$28.87	11.867%	$32.296	$32.30	$32.30	$32.30
Purchase #2	$243.29	9.518%	$266.4463	$266.45	$266.45	$266.40
Purchase #3	$17.59	5.754%	$18.6021	$18.60	$18.60	$18.60
Purchase #4	$170.31	4.593%	$178.1323	$178.13	$178.15	$178.10
Purchase #5	$36.40	3.150%	$37.5466	$37.55	$37.55	$37.50
Purchase #6	$126.31	13.607%	$143.497	$143.50	$143.50	$143.50
Purchase #7	$181.72	8.157%	$196.5429	$196.54	$196.55	$196.50
7 purchase totals =	$804.49		$873.0632	$873.07	$873.10	$872.90