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	$48.99	11.131%	$54.4431	$54.44	$54.45	$54.40
Purchase #2	$215.50	9.296%	$235.5329	$235.53	$235.55	$235.50
Purchase #3	$164.42	4.667%	$172.0935	$172.09	$172.10	$172.10
Purchase #4	$188.75	3.270%	$194.9221	$194.92	$194.90	$194.90
Purchase #5	$10.43	4.265%	$10.8748	$10.87	$10.85	$10.90
Purchase #6	$32.53	7.695%	$35.0332	$35.03	$35.05	$35.00
Purchase #7	$138.79	8.807%	$151.0132	$151.01	$151.00	$151.00
7 purchase totals =	$799.41		$853.9128	$853.89	$853.90	$853.80