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	$164.35	9.321%	$179.6691	$179.67	$179.65	$179.70
Purchase #2	$79.98	13.409%	$90.7045	$90.70	$90.70	$90.70
Purchase #3	$180.74	7.434%	$194.1762	$194.18	$194.20	$194.20
Purchase #4	$60.46	11.391%	$67.347	$67.35	$67.35	$67.30
Purchase #5	$132.86	6.538%	$141.5464	$141.55	$141.55	$141.50
Purchase #6	$243.30	12.564%	$273.8682	$273.87	$273.85	$273.90
Purchase #7	$242.71	10.536%	$268.2819	$268.28	$268.30	$268.30
7 purchase totals =	$1,104.40		$1,215.5933	$1,215.60	$1,215.60	$1,215.60