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	$140.83	3.703%	$146.0449	$146.04	$146.05	$146.00
Purchase #2	$157.82	10.420%	$174.2648	$174.26	$174.25	$174.30
Purchase #3	$109.76	12.800%	$123.8093	$123.81	$123.80	$123.80
Purchase #4	$227.67	11.397%	$253.6175	$253.62	$253.60	$253.60
Purchase #5	$14.66	6.178%	$15.5657	$15.57	$15.55	$15.60
Purchase #6	$128.38	3.795%	$133.252	$133.25	$133.25	$133.30
Purchase #7	$105.86	12.328%	$118.9104	$118.91	$118.90	$118.90
7 purchase totals =	$884.98		$965.4646	$965.46	$965.40	$965.50