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	$73.45	13.225%	$83.1638	$83.16	$83.15	$83.20
Purchase #2	$178.29	5.317%	$187.7697	$187.77	$187.75	$187.80
Purchase #3	$199.45	13.278%	$225.933	$225.93	$225.95	$225.90
Purchase #4	$127.83	11.838%	$142.9625	$142.96	$142.95	$143.00
Purchase #5	$164.76	4.165%	$171.6223	$171.62	$171.60	$171.60
Purchase #6	$104.46	9.628%	$114.5174	$114.52	$114.50	$114.50
Purchase #7	$249.31	12.112%	$279.5064	$279.51	$279.50	$279.50
7 purchase totals =	$1,097.55		$1,205.4751	$1,205.47	$1,205.40	$1,205.50