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	$173.35	13.590%	$196.9083	$196.91	$196.90	$196.90
Purchase #2	$126.95	4.600%	$132.7897	$132.79	$132.80	$132.80
Purchase #3	$9.45	9.717%	$10.3683	$10.37	$10.35	$10.40
Purchase #4	$49.62	11.596%	$55.3739	$55.37	$55.35	$55.40
Purchase #5	$32.63	9.156%	$35.6176	$35.62	$35.60	$35.60
Purchase #6	$130.86	10.206%	$144.2156	$144.22	$144.20	$144.20
Purchase #7	$138.76	8.224%	$150.1716	$150.17	$150.15	$150.20
7 purchase totals =	$661.62		$725.4450	$725.45	$725.35	$725.50