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	$176.86	7.693%	$190.4658	$190.47	$190.45	$190.50
Purchase #2	$142.76	5.137%	$150.0936	$150.09	$150.10	$150.10
Purchase #3	$87.30	10.491%	$96.4586	$96.46	$96.45	$96.50
Purchase #4	$211.29	6.603%	$225.2415	$225.24	$225.25	$225.20
Purchase #5	$81.31	4.598%	$85.0486	$85.05	$85.05	$85.00
Purchase #6	$177.36	12.366%	$199.2923	$199.29	$199.30	$199.30
Purchase #7	$205.89	6.751%	$219.7896	$219.79	$219.80	$219.80
7 purchase totals =	$1,082.77		$1,166.3900	$1,166.39	$1,166.40	$1,166.40