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	$123.67	8.871%	$134.6408	$134.64	$134.65	$134.60
Purchase #2	$54.83	9.171%	$59.8585	$59.86	$59.85	$59.90
Purchase #3	$176.34	3.458%	$182.4378	$182.44	$182.45	$182.40
Purchase #4	$239.59	9.504%	$262.3606	$262.36	$262.35	$262.40
Purchase #5	$76.34	7.799%	$82.2938	$82.29	$82.30	$82.30
Purchase #6	$98.52	9.543%	$107.9218	$107.92	$107.90	$107.90
Purchase #7	$160.58	11.136%	$178.4622	$178.46	$178.45	$178.50
7 purchase totals =	$929.87		$1,007.9755	$1,007.97	$1,007.95	$1,008.00