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	$32.93	6.702%	$35.137	$35.14	$35.15	$35.10
Purchase #2	$54.42	8.433%	$59.0092	$59.01	$59.00	$59.00
Purchase #3	$249.57	3.741%	$258.9064	$258.91	$258.90	$258.90
Purchase #4	$136.60	11.189%	$151.8842	$151.88	$151.90	$151.90
Purchase #5	$69.52	4.548%	$72.6818	$72.68	$72.70	$72.70
Purchase #6	$105.57	3.589%	$109.3589	$109.36	$109.35	$109.40
Purchase #7	$114.35	7.393%	$122.8039	$122.80	$122.80	$122.80
7 purchase totals =	$762.96		$809.7814	$809.78	$809.80	$809.80