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	$181.49	10.526%	$200.5936	$200.59	$200.60	$200.60
Purchase #2	$14.41	11.111%	$16.0111	$16.01	$16.00	$16.00
Purchase #3	$250.90	3.342%	$259.2851	$259.29	$259.30	$259.30
Purchase #4	$18.91	8.504%	$20.5181	$20.52	$20.50	$20.50
Purchase #5	$85.25	8.652%	$92.6258	$92.63	$92.65	$92.60
Purchase #6	$172.72	3.637%	$179.0018	$179.00	$179.00	$179.00
Purchase #7	$176.33	13.695%	$200.4784	$200.48	$200.50	$200.50
7 purchase totals =	$900.01		$968.5139	$968.52	$968.55	$968.50