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	$125.78	5.158%	$132.2677	$132.27	$132.25	$132.30
Purchase #2	$189.88	13.735%	$215.96	$215.96	$215.95	$216.00
Purchase #3	$184.72	4.333%	$192.7239	$192.72	$192.70	$192.70
Purchase #4	$173.45	11.861%	$194.0229	$194.02	$194.00	$194.00
Purchase #5	$100.33	3.241%	$103.5817	$103.58	$103.60	$103.60
Purchase #6	$239.57	9.591%	$262.5472	$262.55	$262.55	$262.50
Purchase #7	$42.52	6.803%	$45.4126	$45.41	$45.40	$45.40
7 purchase totals =	$1,056.25		$1,146.5160	$1,146.51	$1,146.45	$1,146.50