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	$65.47	10.117%	$72.0936	$72.09	$72.10	$72.10
Purchase #2	$54.30	11.626%	$60.6129	$60.61	$60.60	$60.60
Purchase #3	$74.64	13.752%	$84.9045	$84.90	$84.90	$84.90
Purchase #4	$38.30	6.310%	$40.7167	$40.72	$40.70	$40.70
Purchase #5	$159.25	10.335%	$175.7085	$175.71	$175.70	$175.70
Purchase #6	$147.55	7.312%	$158.3389	$158.34	$158.35	$158.30
Purchase #7	$113.98	11.796%	$127.4251	$127.43	$127.45	$127.40
7 purchase totals =	$653.49		$719.8002	$719.80	$719.80	$719.70