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	$162.82	13.729%	$185.1736	$185.17	$185.15	$185.20
Purchase #2	$227.38	10.838%	$252.0234	$252.02	$252.00	$252.00
Purchase #3	$178.25	11.366%	$198.5099	$198.51	$198.50	$198.50
Purchase #4	$215.56	10.668%	$238.5559	$238.56	$238.55	$238.60
Purchase #5	$44.33	9.663%	$48.6136	$48.61	$48.60	$48.60
Purchase #6	$38.76	9.370%	$42.3918	$42.39	$42.40	$42.40
Purchase #7	$6.80	10.626%	$7.5226	$7.52	$7.50	$7.50
7 purchase totals =	$873.90		$972.7908	$972.78	$972.70	$972.80