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	$160.70	9.667%	$176.2349	$176.23	$176.25	$176.20
Purchase #2	$178.60	3.742%	$185.2832	$185.28	$185.30	$185.30
Purchase #3	$233.92	6.388%	$248.8628	$248.86	$248.85	$248.90
Purchase #4	$53.63	10.707%	$59.3722	$59.37	$59.35	$59.40
Purchase #5	$177.84	8.147%	$192.3286	$192.33	$192.35	$192.30
Purchase #6	$112.46	11.445%	$125.331	$125.33	$125.35	$125.30
Purchase #7	$82.56	13.280%	$93.524	$93.52	$93.50	$93.50
7 purchase totals =	$999.71		$1,080.9367	$1,080.92	$1,080.95	$1,080.90