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	$116.27	6.580%	$123.9206	$123.92	$123.90	$123.90
Purchase #2	$246.70	6.781%	$263.4287	$263.43	$263.45	$263.40
Purchase #3	$46.69	5.183%	$49.1099	$49.11	$49.10	$49.10
Purchase #4	$39.92	10.118%	$43.9591	$43.96	$43.95	$44.00
Purchase #5	$159.31	10.160%	$175.4959	$175.50	$175.50	$175.50
Purchase #6	$194.39	3.317%	$200.8379	$200.84	$200.85	$200.80
Purchase #7	$164.68	12.491%	$185.2502	$185.25	$185.25	$185.30
7 purchase totals =	$967.96		$1,042.0023	$1,042.01	$1,042.00	$1,042.00