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	$248.76	5.542%	$262.5463	$262.55	$262.55	$262.50
Purchase #2	$49.99	6.861%	$53.4198	$53.42	$53.40	$53.40
Purchase #3	$79.35	12.262%	$89.0799	$89.08	$89.10	$89.10
Purchase #4	$163.91	12.473%	$184.3545	$184.35	$184.35	$184.40
Purchase #5	$210.88	13.127%	$238.5622	$238.56	$238.55	$238.60
Purchase #6	$57.61	3.490%	$59.6206	$59.62	$59.60	$59.60
Purchase #7	$113.83	6.408%	$121.1242	$121.12	$121.10	$121.10
7 purchase totals =	$924.33		$1,008.7075	$1,008.70	$1,008.65	$1,008.70