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	$43.28	4.411%	$45.1891	$45.19	$45.20	$45.20
Purchase #2	$28.57	9.134%	$31.1796	$31.18	$31.20	$31.20
Purchase #3	$68.75	4.615%	$71.9228	$71.92	$71.90	$71.90
Purchase #4	$115.64	9.854%	$127.0352	$127.04	$127.05	$127.00
Purchase #5	$48.45	4.424%	$50.5934	$50.59	$50.60	$50.60
Purchase #6	$132.49	4.823%	$138.88	$138.88	$138.90	$138.90
Purchase #7	$194.87	13.823%	$221.8069	$221.81	$221.80	$221.80
7 purchase totals =	$632.05		$686.6070	$686.61	$686.65	$686.60