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	$175.77	9.407%	$192.3047	$192.30	$192.30	$192.30
Purchase #2	$124.55	10.243%	$137.3077	$137.31	$137.30	$137.30
Purchase #3	$176.31	3.652%	$182.7488	$182.75	$182.75	$182.70
Purchase #4	$197.95	5.582%	$208.9996	$209.00	$209.00	$209.00
Purchase #5	$98.93	12.620%	$111.415	$111.42	$111.40	$111.40
Purchase #6	$80.25	4.456%	$83.8259	$83.83	$83.85	$83.80
Purchase #7	$79.51	3.690%	$82.4439	$82.44	$82.45	$82.40
7 purchase totals =	$933.27		$999.0456	$999.05	$999.05	$998.90