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	$156.81	11.234%	$174.426	$174.43	$174.45	$174.40
Purchase #2	$156.59	6.829%	$167.2835	$167.28	$167.30	$167.30
Purchase #3	$109.62	13.828%	$124.7783	$124.78	$124.80	$124.80
Purchase #4	$30.76	12.224%	$34.5201	$34.52	$34.50	$34.50
Purchase #5	$38.36	13.436%	$43.514	$43.51	$43.50	$43.50
Purchase #6	$81.38	13.564%	$92.4184	$92.42	$92.40	$92.40
Purchase #7	$108.56	9.784%	$119.1815	$119.18	$119.20	$119.20
7 purchase totals =	$682.08		$756.1218	$756.12	$756.15	$756.10