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	$153.74	3.303%	$158.818	$158.82	$158.80	$158.80
Purchase #2	$185.97	5.718%	$196.6038	$196.60	$196.60	$196.60
Purchase #3	$79.92	11.762%	$89.3202	$89.32	$89.30	$89.30
Purchase #4	$113.38	4.693%	$118.7009	$118.70	$118.70	$118.70
Purchase #5	$191.33	9.231%	$208.9917	$208.99	$209.00	$209.00
Purchase #6	$149.29	3.199%	$154.0658	$154.07	$154.05	$154.10
Purchase #7	$117.53	12.771%	$132.5398	$132.54	$132.55	$132.50
7 purchase totals =	$991.16		$1,059.0402	$1,059.04	$1,059.00	$1,059.00