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	$182.51	7.463%	$196.1307	$196.13	$196.15	$196.10
Purchase #2	$62.60	5.250%	$65.8865	$65.89	$65.90	$65.90
Purchase #3	$129.39	9.520%	$141.7079	$141.71	$141.70	$141.70
Purchase #4	$246.41	12.207%	$276.4893	$276.49	$276.50	$276.50
Purchase #5	$70.89	7.177%	$75.9778	$75.98	$76.00	$76.00
Purchase #6	$104.47	13.284%	$118.3478	$118.35	$118.35	$118.30
Purchase #7	$114.81	7.757%	$123.7158	$123.72	$123.70	$123.70
7 purchase totals =	$911.08		$998.2558	$998.27	$998.30	$998.20