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	$142.41	11.270%	$158.4596	$158.46	$158.45	$158.50
Purchase #2	$122.62	9.615%	$134.4099	$134.41	$134.40	$134.40
Purchase #3	$215.30	10.344%	$237.5706	$237.57	$237.55	$237.60
Purchase #4	$178.30	10.415%	$196.8699	$196.87	$196.85	$196.90
Purchase #5	$93.80	5.548%	$99.004	$99.00	$99.00	$99.00
Purchase #6	$109.47	10.362%	$120.8133	$120.81	$120.80	$120.80
Purchase #7	$135.86	9.731%	$149.0805	$149.08	$149.10	$149.10
7 purchase totals =	$997.76		$1,096.2078	$1,096.20	$1,096.15	$1,096.30