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	$99.28	11.615%	$110.8114	$110.81	$110.80	$110.80
Purchase #2	$190.52	7.678%	$205.1481	$205.15	$205.15	$205.10
Purchase #3	$221.95	11.863%	$248.2799	$248.28	$248.30	$248.30
Purchase #4	$91.59	9.734%	$100.5054	$100.51	$100.50	$100.50
Purchase #5	$158.43	10.839%	$175.6022	$175.60	$175.60	$175.60
Purchase #6	$82.70	4.694%	$86.5819	$86.58	$86.60	$86.60
Purchase #7	$163.31	11.440%	$181.9927	$181.99	$182.00	$182.00
7 purchase totals =	$1,007.78		$1,108.9216	$1,108.92	$1,108.95	$1,108.90