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	$83.82	10.517%	$92.6353	$92.64	$92.65	$92.60
Purchase #2	$217.88	12.694%	$245.5377	$245.54	$245.55	$245.50
Purchase #3	$176.94	3.682%	$183.4549	$183.45	$183.45	$183.50
Purchase #4	$106.58	5.519%	$112.4622	$112.46	$112.45	$112.50
Purchase #5	$198.57	12.240%	$222.875	$222.88	$222.90	$222.90
Purchase #6	$216.96	6.320%	$230.6719	$230.67	$230.65	$230.70
Purchase #7	$50.29	11.833%	$56.2408	$56.24	$56.25	$56.20
7 purchase totals =	$1,051.04		$1,143.8778	$1,143.88	$1,143.90	$1,143.90