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	$153.81	13.761%	$174.9758	$174.98	$175.00	$175.00
Purchase #2	$45.62	6.351%	$48.5173	$48.52	$48.50	$48.50
Purchase #3	$132.89	7.177%	$142.4275	$142.43	$142.45	$142.40
Purchase #4	$51.26	4.321%	$53.4749	$53.47	$53.45	$53.50
Purchase #5	$189.41	7.322%	$203.2786	$203.28	$203.30	$203.30
Purchase #6	$35.99	9.617%	$39.4512	$39.45	$39.45	$39.50
Purchase #7	$49.52	9.722%	$54.3343	$54.33	$54.35	$54.30
7 purchase totals =	$658.50		$716.4596	$716.46	$716.50	$716.50