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	$199.85	8.207%	$216.2517	$216.25	$216.25	$216.30
Purchase #2	$178.83	12.225%	$200.692	$200.69	$200.70	$200.70
Purchase #3	$171.94	10.661%	$190.2705	$190.27	$190.25	$190.30
Purchase #4	$237.96	7.264%	$255.2454	$255.25	$255.25	$255.20
Purchase #5	$38.49	12.294%	$43.222	$43.22	$43.20	$43.20
Purchase #6	$113.69	4.190%	$118.4536	$118.45	$118.45	$118.50
Purchase #7	$98.37	8.237%	$106.4727	$106.47	$106.45	$106.50
7 purchase totals =	$1,039.13		$1,130.6079	$1,130.60	$1,130.55	$1,130.70