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	$46.30	11.168%	$51.4708	$51.47	$51.45	$51.50
Purchase #2	$163.78	4.689%	$171.4596	$171.46	$171.45	$171.50
Purchase #3	$153.52	12.713%	$173.037	$173.04	$173.05	$173.00
Purchase #4	$245.99	6.599%	$262.2229	$262.22	$262.20	$262.20
Purchase #5	$67.62	4.364%	$70.5709	$70.57	$70.55	$70.60
Purchase #6	$133.58	7.475%	$143.5651	$143.57	$143.55	$143.60
Purchase #7	$196.34	6.636%	$209.3691	$209.37	$209.35	$209.40
7 purchase totals =	$1,007.13		$1,081.6954	$1,081.70	$1,081.60	$1,081.80