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	$139.50	5.554%	$147.2478	$147.25	$147.25	$147.20
Purchase #2	$88.77	11.262%	$98.7673	$98.77	$98.75	$98.80
Purchase #3	$221.75	13.691%	$252.1098	$252.11	$252.10	$252.10
Purchase #4	$62.95	7.191%	$67.4767	$67.48	$67.50	$67.50
Purchase #5	$45.45	13.609%	$51.6353	$51.64	$51.65	$51.60
Purchase #6	$47.87	7.532%	$51.4756	$51.48	$51.50	$51.50
Purchase #7	$53.31	6.654%	$56.8572	$56.86	$56.85	$56.90
7 purchase totals =	$659.60		$725.5697	$725.59	$725.60	$725.60