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	$207.62	10.223%	$228.845	$228.85	$228.85	$228.80
Purchase #2	$241.69	12.332%	$271.4952	$271.50	$271.50	$271.50
Purchase #3	$227.77	4.761%	$238.6141	$238.61	$238.60	$238.60
Purchase #4	$26.58	4.483%	$27.7716	$27.77	$27.75	$27.80
Purchase #5	$72.92	9.198%	$79.6272	$79.63	$79.65	$79.60
Purchase #6	$227.86	8.313%	$246.802	$246.80	$246.80	$246.80
Purchase #7	$83.81	6.581%	$89.3255	$89.33	$89.35	$89.30
7 purchase totals =	$1,088.25		$1,182.4806	$1,182.49	$1,182.50	$1,182.40