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	$248.62	10.118%	$273.7754	$273.78	$273.80	$273.80
Purchase #2	$210.39	12.379%	$236.4342	$236.43	$236.45	$236.40
Purchase #3	$20.48	9.112%	$22.3461	$22.35	$22.35	$22.30
Purchase #4	$46.86	12.777%	$52.8473	$52.85	$52.85	$52.80
Purchase #5	$143.25	13.683%	$162.8509	$162.85	$162.85	$162.90
Purchase #6	$114.46	8.791%	$124.5222	$124.52	$124.50	$124.50
Purchase #7	$249.32	4.123%	$259.5995	$259.60	$259.60	$259.60
7 purchase totals =	$1,033.38		$1,132.3756	$1,132.38	$1,132.40	$1,132.30