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	$182.56	13.167%	$206.5977	$206.60	$206.60	$206.60
Purchase #2	$164.80	5.273%	$173.4899	$173.49	$173.50	$173.50
Purchase #3	$18.56	9.628%	$20.347	$20.35	$20.35	$20.30
Purchase #4	$182.46	7.818%	$196.7247	$196.72	$196.70	$196.70
Purchase #5	$141.55	12.675%	$159.4915	$159.49	$159.50	$159.50
Purchase #6	$44.54	12.491%	$50.1035	$50.10	$50.10	$50.10
Purchase #7	$210.58	7.601%	$226.5862	$226.59	$226.60	$226.60
7 purchase totals =	$945.05		$1,033.3405	$1,033.34	$1,033.35	$1,033.30