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	$233.49	11.763%	$260.9554	$260.96	$260.95	$261.00
Purchase #2	$73.72	6.838%	$78.761	$78.76	$78.75	$78.80
Purchase #3	$126.82	11.808%	$141.7949	$141.79	$141.80	$141.80
Purchase #4	$102.37	8.700%	$111.2762	$111.28	$111.30	$111.30
Purchase #5	$76.57	3.331%	$79.1205	$79.12	$79.10	$79.10
Purchase #6	$153.43	5.854%	$162.4118	$162.41	$162.40	$162.40
Purchase #7	$159.94	6.397%	$170.1714	$170.17	$170.15	$170.20
7 purchase totals =	$926.34		$1,004.4912	$1,004.49	$1,004.45	$1,004.60