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	$157.25	4.823%	$164.8342	$164.83	$164.85	$164.80
Purchase #2	$201.73	8.818%	$219.5186	$219.52	$219.50	$219.50
Purchase #3	$248.88	3.120%	$256.6451	$256.65	$256.65	$256.60
Purchase #4	$175.83	9.205%	$192.0152	$192.02	$192.00	$192.00
Purchase #5	$22.43	8.198%	$24.2688	$24.27	$24.25	$24.30
Purchase #6	$143.25	13.346%	$162.3681	$162.37	$162.35	$162.40
Purchase #7	$60.27	3.437%	$62.3415	$62.34	$62.35	$62.30
7 purchase totals =	$1,009.64		$1,081.9915	$1,082.00	$1,081.95	$1,081.90