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	$156.61	6.783%	$167.2329	$167.23	$167.25	$167.20
Purchase #2	$21.96	11.685%	$24.526	$24.53	$24.55	$24.50
Purchase #3	$118.62	8.355%	$128.5307	$128.53	$128.55	$128.50
Purchase #4	$21.79	9.444%	$23.8478	$23.85	$23.85	$23.80
Purchase #5	$54.82	7.645%	$59.011	$59.01	$59.00	$59.00
Purchase #6	$153.56	9.660%	$168.3939	$168.39	$168.40	$168.40
Purchase #7	$133.65	5.748%	$141.3322	$141.33	$141.35	$141.30
7 purchase totals =	$661.01		$712.8745	$712.87	$712.95	$712.70