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	$192.80	12.474%	$216.8499	$216.85	$216.85	$216.80
Purchase #2	$89.58	7.368%	$96.1803	$96.18	$96.20	$96.20
Purchase #3	$128.52	6.835%	$137.3043	$137.30	$137.30	$137.30
Purchase #4	$128.56	12.782%	$144.9925	$144.99	$145.00	$145.00
Purchase #5	$46.86	9.149%	$51.1472	$51.15	$51.15	$51.10
Purchase #6	$123.95	12.699%	$139.6904	$139.69	$139.70	$139.70
Purchase #7	$222.82	4.792%	$233.4975	$233.50	$233.50	$233.50
7 purchase totals =	$933.09		$1,019.6621	$1,019.66	$1,019.70	$1,019.60