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	$117.83	13.127%	$133.2975	$133.30	$133.30	$133.30
Purchase #2	$164.39	10.249%	$181.2383	$181.24	$181.25	$181.20
Purchase #3	$165.83	6.423%	$176.4813	$176.48	$176.50	$176.50
Purchase #4	$128.29	11.314%	$142.8047	$142.80	$142.80	$142.80
Purchase #5	$237.92	3.175%	$245.474	$245.47	$245.45	$245.50
Purchase #6	$68.52	13.466%	$77.7469	$77.75	$77.75	$77.70
Purchase #7	$134.41	13.212%	$152.1682	$152.17	$152.15	$152.20
7 purchase totals =	$1,017.19		$1,109.2109	$1,109.21	$1,109.20	$1,109.20