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	$158.40	6.525%	$168.7356	$168.74	$168.75	$168.70
Purchase #2	$26.92	9.214%	$29.4004	$29.40	$29.40	$29.40
Purchase #3	$79.58	4.793%	$83.3943	$83.39	$83.40	$83.40
Purchase #4	$181.73	8.114%	$196.4756	$196.48	$196.50	$196.50
Purchase #5	$181.78	4.491%	$189.9437	$189.94	$189.95	$189.90
Purchase #6	$139.32	8.752%	$151.5133	$151.51	$151.50	$151.50
Purchase #7	$234.26	3.247%	$241.8664	$241.87	$241.85	$241.90
7 purchase totals =	$1,001.99		$1,061.3293	$1,061.33	$1,061.35	$1,061.30