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	$77.25	7.218%	$82.8259	$82.83	$82.85	$82.80
Purchase #2	$21.49	12.132%	$24.0972	$24.10	$24.10	$24.10
Purchase #3	$167.87	10.453%	$185.4175	$185.42	$185.40	$185.40
Purchase #4	$75.26	9.668%	$82.5361	$82.54	$82.55	$82.50
Purchase #5	$107.60	7.437%	$115.6022	$115.60	$115.60	$115.60
Purchase #6	$111.96	5.731%	$118.3764	$118.38	$118.40	$118.40
Purchase #7	$157.42	12.728%	$177.4564	$177.46	$177.45	$177.50
7 purchase totals =	$718.85		$786.3117	$786.33	$786.35	$786.30