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	$192.73	9.327%	$210.7059	$210.71	$210.70	$210.70
Purchase #2	$78.59	12.760%	$88.6181	$88.62	$88.60	$88.60
Purchase #3	$196.38	12.603%	$221.1298	$221.13	$221.15	$221.10
Purchase #4	$51.39	8.249%	$55.6292	$55.63	$55.65	$55.60
Purchase #5	$116.73	9.475%	$127.7902	$127.79	$127.80	$127.80
Purchase #6	$153.86	3.288%	$158.9189	$158.92	$158.90	$158.90
Purchase #7	$43.93	5.123%	$46.1805	$46.18	$46.20	$46.20
7 purchase totals =	$833.61		$908.9726	$908.98	$909.00	$908.90