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	$219.68	12.138%	$246.3448	$246.34	$246.35	$246.30
Purchase #2	$39.95	6.434%	$42.5204	$42.52	$42.50	$42.50
Purchase #3	$182.53	13.301%	$206.8083	$206.81	$206.80	$206.80
Purchase #4	$77.82	4.724%	$81.4962	$81.50	$81.50	$81.50
Purchase #5	$14.62	6.250%	$15.5338	$15.53	$15.55	$15.50
Purchase #6	$19.62	6.564%	$20.9079	$20.91	$20.90	$20.90
Purchase #7	$74.83	10.313%	$82.5472	$82.55	$82.55	$82.50
7 purchase totals =	$629.05		$696.1586	$696.16	$696.15	$696.00