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	$125.58	13.862%	$142.9879	$142.99	$143.00	$143.00
Purchase #2	$71.34	11.541%	$79.5733	$79.57	$79.55	$79.60
Purchase #3	$250.43	6.575%	$266.8958	$266.90	$266.90	$266.90
Purchase #4	$154.90	11.866%	$173.2804	$173.28	$173.30	$173.30
Purchase #5	$137.40	13.236%	$155.5863	$155.59	$155.60	$155.60
Purchase #6	$141.98	7.153%	$152.1358	$152.14	$152.15	$152.10
Purchase #7	$133.72	6.216%	$142.032	$142.03	$142.05	$142.00
7 purchase totals =	$1,015.35		$1,112.4915	$1,112.50	$1,112.55	$1,112.50