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	$179.32	3.444%	$185.4958	$185.50	$185.50	$185.50
Purchase #2	$166.54	4.357%	$173.7961	$173.80	$173.80	$173.80
Purchase #3	$79.45	6.321%	$84.472	$84.47	$84.45	$84.50
Purchase #4	$54.94	12.742%	$61.9405	$61.94	$61.95	$61.90
Purchase #5	$160.47	10.275%	$176.9583	$176.96	$176.95	$177.00
Purchase #6	$154.32	12.796%	$174.0668	$174.07	$174.05	$174.10
Purchase #7	$201.79	10.208%	$222.3887	$222.39	$222.40	$222.40
7 purchase totals =	$996.83		$1,079.1182	$1,079.13	$1,079.10	$1,079.20