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	$236.52	5.345%	$249.162	$249.16	$249.15	$249.20
Purchase #2	$50.40	6.812%	$53.8332	$53.83	$53.85	$53.80
Purchase #3	$229.82	11.394%	$256.0057	$256.01	$256.00	$256.00
Purchase #4	$191.47	9.514%	$209.6865	$209.69	$209.70	$209.70
Purchase #5	$238.82	5.427%	$251.7808	$251.78	$251.80	$251.80
Purchase #6	$19.53	8.830%	$21.2545	$21.25	$21.25	$21.30
Purchase #7	$10.38	6.820%	$11.0879	$11.09	$11.10	$11.10
7 purchase totals =	$976.94		$1,052.8106	$1,052.81	$1,052.85	$1,052.90