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	$136.49	13.597%	$155.0485	$155.05	$155.05	$155.00
Purchase #2	$214.71	3.606%	$222.4524	$222.45	$222.45	$222.50
Purchase #3	$247.54	7.650%	$266.4768	$266.48	$266.50	$266.50
Purchase #4	$83.77	12.616%	$94.3384	$94.34	$94.35	$94.30
Purchase #5	$111.42	8.141%	$120.4907	$120.49	$120.50	$120.50
Purchase #6	$30.69	4.589%	$32.0984	$32.10	$32.10	$32.10
Purchase #7	$226.42	10.819%	$250.9164	$250.92	$250.90	$250.90
7 purchase totals =	$1,051.04		$1,141.8216	$1,141.83	$1,141.85	$1,141.80