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	$111.55	10.505%	$123.2683	$123.27	$123.25	$123.30
Purchase #2	$196.28	7.760%	$211.5113	$211.51	$211.50	$211.50
Purchase #3	$147.91	8.623%	$160.6643	$160.66	$160.65	$160.70
Purchase #4	$205.78	8.375%	$223.0141	$223.01	$223.00	$223.00
Purchase #5	$210.58	3.314%	$217.5586	$217.56	$217.55	$217.60
Purchase #6	$143.35	7.256%	$153.7515	$153.75	$153.75	$153.80
Purchase #7	$78.25	4.685%	$81.916	$81.92	$81.90	$81.90
7 purchase totals =	$1,093.70		$1,171.6841	$1,171.68	$1,171.60	$1,171.80