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	$187.51	7.104%	$200.8307	$200.83	$200.85	$200.80
Purchase #2	$80.60	5.173%	$84.7694	$84.77	$84.75	$84.80
Purchase #3	$79.96	4.416%	$83.491	$83.49	$83.50	$83.50
Purchase #4	$7.78	9.105%	$8.4884	$8.49	$8.50	$8.50
Purchase #5	$240.56	9.188%	$262.6627	$262.66	$262.65	$262.70
Purchase #6	$126.88	4.446%	$132.5211	$132.52	$132.50	$132.50
Purchase #7	$137.53	13.803%	$156.5133	$156.51	$156.50	$156.50
7 purchase totals =	$860.82		$929.2766	$929.27	$929.25	$929.30