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	$117.94	10.866%	$130.7554	$130.76	$130.75	$130.80
Purchase #2	$72.62	12.807%	$81.9204	$81.92	$81.90	$81.90
Purchase #3	$20.83	3.741%	$21.6093	$21.61	$21.60	$21.60
Purchase #4	$108.58	3.622%	$112.5128	$112.51	$112.50	$112.50
Purchase #5	$104.28	10.117%	$114.83	$114.83	$114.85	$114.80
Purchase #6	$235.88	5.227%	$248.2094	$248.21	$248.20	$248.20
Purchase #7	$198.65	6.579%	$211.7192	$211.72	$211.70	$211.70
7 purchase totals =	$858.78		$921.5565	$921.56	$921.50	$921.50