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	$83.54	9.436%	$91.4228	$91.42	$91.40	$91.40
Purchase #2	$133.87	11.850%	$149.7336	$149.73	$149.75	$149.70
Purchase #3	$221.73	5.377%	$233.6524	$233.65	$233.65	$233.70
Purchase #4	$228.94	12.182%	$256.8295	$256.83	$256.85	$256.80
Purchase #5	$113.30	5.448%	$119.4726	$119.47	$119.45	$119.50
Purchase #6	$239.52	3.283%	$247.3834	$247.38	$247.40	$247.40
Purchase #7	$80.47	6.667%	$85.8349	$85.83	$85.85	$85.80
7 purchase totals =	$1,101.37		$1,184.3292	$1,184.31	$1,184.35	$1,184.30