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	$192.83	3.198%	$198.9967	$199.00	$199.00	$199.00
Purchase #2	$205.94	10.635%	$227.8417	$227.84	$227.85	$227.80
Purchase #3	$82.45	8.318%	$89.3082	$89.31	$89.30	$89.30
Purchase #4	$189.83	3.649%	$196.7569	$196.76	$196.75	$196.80
Purchase #5	$59.63	6.801%	$63.6854	$63.69	$63.70	$63.70
Purchase #6	$190.62	8.858%	$207.5051	$207.51	$207.50	$207.50
Purchase #7	$78.72	10.606%	$87.069	$87.07	$87.05	$87.10
7 purchase totals =	$1,000.02		$1,071.1630	$1,071.18	$1,071.15	$1,071.20