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	$142.46	10.151%	$156.9211	$156.92	$156.90	$156.90
Purchase #2	$90.44	4.807%	$94.7875	$94.79	$94.80	$94.80
Purchase #3	$42.54	5.269%	$44.7814	$44.78	$44.80	$44.80
Purchase #4	$52.32	5.137%	$55.0077	$55.01	$55.00	$55.00
Purchase #5	$215.71	8.406%	$233.8426	$233.84	$233.85	$233.80
Purchase #6	$144.82	5.773%	$153.1805	$153.18	$153.20	$153.20
Purchase #7	$84.58	6.710%	$90.2553	$90.26	$90.25	$90.30
7 purchase totals =	$772.87		$828.7761	$828.78	$828.80	$828.80