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	$154.51	11.496%	$172.2725	$172.27	$172.25	$172.30
Purchase #2	$132.27	9.714%	$145.1187	$145.12	$145.10	$145.10
Purchase #3	$75.70	9.455%	$82.8574	$82.86	$82.85	$82.90
Purchase #4	$70.45	11.546%	$78.5842	$78.58	$78.60	$78.60
Purchase #5	$109.77	4.633%	$114.8556	$114.86	$114.85	$114.90
Purchase #6	$55.70	7.264%	$59.746	$59.75	$59.75	$59.70
Purchase #7	$145.46	7.672%	$156.6197	$156.62	$156.60	$156.60
7 purchase totals =	$743.86		$810.0541	$810.06	$810.00	$810.10