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	$43.26	3.585%	$44.8109	$44.81	$44.80	$44.80
Purchase #2	$178.59	11.177%	$198.551	$198.55	$198.55	$198.60
Purchase #3	$98.90	6.337%	$105.1673	$105.17	$105.15	$105.20
Purchase #4	$184.75	13.573%	$209.8261	$209.83	$209.85	$209.80
Purchase #5	$116.25	10.661%	$128.6434	$128.64	$128.65	$128.60
Purchase #6	$6.87	5.145%	$7.2235	$7.22	$7.20	$7.20
Purchase #7	$160.45	7.339%	$172.2254	$172.23	$172.25	$172.20
7 purchase totals =	$789.07		$866.4476	$866.45	$866.45	$866.40