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	$192.25	3.717%	$199.3959	$199.40	$199.40	$199.40
Purchase #2	$190.61	5.233%	$200.5846	$200.58	$200.60	$200.60
Purchase #3	$133.56	4.451%	$139.5048	$139.50	$139.50	$139.50
Purchase #4	$105.41	10.612%	$116.5961	$116.60	$116.60	$116.60
Purchase #5	$94.56	13.426%	$107.2556	$107.26	$107.25	$107.30
Purchase #6	$247.45	8.511%	$268.5105	$268.51	$268.50	$268.50
Purchase #7	$142.92	9.732%	$156.829	$156.83	$156.85	$156.80
7 purchase totals =	$1,106.76		$1,188.6765	$1,188.68	$1,188.70	$1,188.70