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	$243.45	3.612%	$252.2434	$252.24	$252.25	$252.20
Purchase #2	$135.52	4.352%	$141.4178	$141.42	$141.40	$141.40
Purchase #3	$48.95	11.661%	$54.6581	$54.66	$54.65	$54.70
Purchase #4	$131.91	8.381%	$142.9654	$142.97	$142.95	$143.00
Purchase #5	$33.26	11.600%	$37.1182	$37.12	$37.10	$37.10
Purchase #6	$234.46	11.724%	$261.9481	$261.95	$261.95	$261.90
Purchase #7	$175.77	11.411%	$195.8271	$195.83	$195.85	$195.80
7 purchase totals =	$1,003.32		$1,086.1781	$1,086.19	$1,086.15	$1,086.10