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	$87.48	10.528%	$96.6899	$96.69	$96.70	$96.70
Purchase #2	$99.80	12.491%	$112.266	$112.27	$112.25	$112.30
Purchase #3	$241.55	12.344%	$271.3669	$271.37	$271.35	$271.40
Purchase #4	$165.66	12.800%	$186.8645	$186.86	$186.85	$186.90
Purchase #5	$18.42	13.270%	$20.8643	$20.86	$20.85	$20.90
Purchase #6	$50.50	4.456%	$52.7503	$52.75	$52.75	$52.80
Purchase #7	$89.33	3.668%	$92.6066	$92.61	$92.60	$92.60
7 purchase totals =	$752.74		$833.4085	$833.41	$833.35	$833.60