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	$13.40	6.495%	$14.2703	$14.27	$14.25	$14.30
Purchase #2	$143.48	5.862%	$151.8908	$151.89	$151.90	$151.90
Purchase #3	$48.66	9.351%	$53.2102	$53.21	$53.20	$53.20
Purchase #4	$43.78	7.856%	$47.2194	$47.22	$47.20	$47.20
Purchase #5	$19.54	13.263%	$22.1316	$22.13	$22.15	$22.10
Purchase #6	$11.33	6.489%	$12.0652	$12.07	$12.05	$12.10
Purchase #7	$116.77	5.868%	$123.6221	$123.62	$123.60	$123.60
7 purchase totals =	$396.96		$424.4096	$424.41	$424.35	$424.40