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	$38.47	13.705%	$43.7423	$43.74	$43.75	$43.70
Purchase #2	$181.73	5.794%	$192.2594	$192.26	$192.25	$192.30
Purchase #3	$148.79	4.162%	$154.9826	$154.98	$155.00	$155.00
Purchase #4	$56.78	4.236%	$59.1852	$59.19	$59.20	$59.20
Purchase #5	$114.45	5.128%	$120.319	$120.32	$120.30	$120.30
Purchase #6	$117.80	5.601%	$124.398	$124.40	$124.40	$124.40
Purchase #7	$63.89	13.688%	$72.6353	$72.64	$72.65	$72.60
7 purchase totals =	$721.91		$767.5218	$767.53	$767.55	$767.50