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	$141.38	6.247%	$150.212	$150.21	$150.20	$150.20
Purchase #2	$143.97	12.838%	$162.4529	$162.45	$162.45	$162.50
Purchase #3	$149.72	4.510%	$156.4724	$156.47	$156.45	$156.50
Purchase #4	$191.77	4.170%	$199.7668	$199.77	$199.75	$199.80
Purchase #5	$98.94	13.628%	$112.4235	$112.42	$112.40	$112.40
Purchase #6	$183.88	11.688%	$205.3719	$205.37	$205.35	$205.40
Purchase #7	$111.76	5.805%	$118.2477	$118.25	$118.25	$118.20
7 purchase totals =	$1,021.42		$1,104.9472	$1,104.94	$1,104.85	$1,105.00