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	$156.50	3.767%	$162.3954	$162.40	$162.40	$162.40
Purchase #2	$103.78	7.425%	$111.4857	$111.49	$111.50	$111.50
Purchase #3	$29.95	3.131%	$30.8877	$30.89	$30.90	$30.90
Purchase #4	$240.39	6.416%	$255.8134	$255.81	$255.80	$255.80
Purchase #5	$133.94	6.802%	$143.0506	$143.05	$143.05	$143.10
Purchase #6	$151.96	4.737%	$159.1583	$159.16	$159.15	$159.20
Purchase #7	$122.91	7.809%	$132.508	$132.51	$132.50	$132.50
7 purchase totals =	$939.43		$995.2991	$995.31	$995.30	$995.40