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	$24.81	3.339%	$25.6384	$25.64	$25.65	$25.60
Purchase #2	$87.32	4.659%	$91.3882	$91.39	$91.40	$91.40
Purchase #3	$96.77	12.584%	$108.9475	$108.95	$108.95	$108.90
Purchase #4	$31.48	12.647%	$35.4613	$35.46	$35.45	$35.50
Purchase #5	$11.54	10.143%	$12.7105	$12.71	$12.70	$12.70
Purchase #6	$209.85	5.111%	$220.5754	$220.58	$220.60	$220.60
Purchase #7	$81.88	9.773%	$89.8821	$89.88	$89.90	$89.90
7 purchase totals =	$543.65		$584.6034	$584.61	$584.65	$584.60