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	$173.83	4.783%	$182.1443	$182.14	$182.15	$182.10
Purchase #2	$104.92	5.373%	$110.5574	$110.56	$110.55	$110.60
Purchase #3	$38.60	7.744%	$41.5892	$41.59	$41.60	$41.60
Purchase #4	$196.45	13.444%	$222.8607	$222.86	$222.85	$222.90
Purchase #5	$157.35	11.571%	$175.557	$175.56	$175.55	$175.60
Purchase #6	$138.40	12.493%	$155.6903	$155.69	$155.70	$155.70
Purchase #7	$172.47	4.525%	$180.2743	$180.27	$180.25	$180.30
7 purchase totals =	$982.02		$1,068.6732	$1,068.67	$1,068.65	$1,068.80