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	$122.93	4.171%	$128.0574	$128.06	$128.05	$128.10
Purchase #2	$113.36	4.585%	$118.5576	$118.56	$118.55	$118.60
Purchase #3	$16.30	7.286%	$17.4876	$17.49	$17.50	$17.50
Purchase #4	$231.86	9.453%	$253.7777	$253.78	$253.80	$253.80
Purchase #5	$235.59	10.557%	$260.4612	$260.46	$260.45	$260.50
Purchase #6	$126.58	4.825%	$132.6875	$132.69	$132.70	$132.70
Purchase #7	$170.89	10.868%	$189.4623	$189.46	$189.45	$189.50
7 purchase totals =	$1,017.51		$1,100.4913	$1,100.50	$1,100.50	$1,100.70