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	$208.26	12.514%	$234.3217	$234.32	$234.30	$234.30
Purchase #2	$74.40	5.628%	$78.5872	$78.59	$78.60	$78.60
Purchase #3	$95.37	3.341%	$98.5563	$98.56	$98.55	$98.60
Purchase #4	$142.28	4.249%	$148.3255	$148.33	$148.35	$148.30
Purchase #5	$106.74	7.337%	$114.5715	$114.57	$114.55	$114.60
Purchase #6	$222.28	8.839%	$241.9273	$241.93	$241.95	$241.90
Purchase #7	$90.56	3.116%	$93.3818	$93.38	$93.40	$93.40
7 purchase totals =	$939.89		$1,009.6713	$1,009.68	$1,009.70	$1,009.70