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	$75.25	4.516%	$78.6483	$78.65	$78.65	$78.60
Purchase #2	$118.73	7.191%	$127.2679	$127.27	$127.25	$127.30
Purchase #3	$155.35	5.105%	$163.2806	$163.28	$163.30	$163.30
Purchase #4	$158.79	11.518%	$177.0794	$177.08	$177.10	$177.10
Purchase #5	$54.50	3.625%	$56.4756	$56.48	$56.50	$56.50
Purchase #6	$215.40	7.150%	$230.8011	$230.80	$230.80	$230.80
Purchase #7	$147.90	13.778%	$168.2777	$168.28	$168.30	$168.30
7 purchase totals =	$925.92		$1,001.8306	$1,001.84	$1,001.90	$1,001.90