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	$154.75	7.249%	$165.9678	$165.97	$165.95	$166.00
Purchase #2	$133.91	5.223%	$140.9041	$140.90	$140.90	$140.90
Purchase #3	$88.52	5.579%	$93.4585	$93.46	$93.45	$93.50
Purchase #4	$159.62	4.853%	$167.3664	$167.37	$167.35	$167.40
Purchase #5	$98.51	13.553%	$111.8611	$111.86	$111.85	$111.90
Purchase #6	$155.67	5.583%	$164.3611	$164.36	$164.35	$164.40
Purchase #7	$227.41	4.538%	$237.7299	$237.73	$237.75	$237.70
7 purchase totals =	$1,018.39		$1,081.6489	$1,081.65	$1,081.60	$1,081.80