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	$54.75	5.348%	$57.678	$57.68	$57.70	$57.70
Purchase #2	$11.51	6.285%	$12.2334	$12.23	$12.25	$12.20
Purchase #3	$139.54	8.448%	$151.3283	$151.33	$151.35	$151.30
Purchase #4	$109.78	9.738%	$120.4704	$120.47	$120.45	$120.50
Purchase #5	$151.84	10.145%	$167.2442	$167.24	$167.25	$167.20
Purchase #6	$156.59	7.476%	$168.2967	$168.30	$168.30	$168.30
Purchase #7	$121.83	12.821%	$137.4498	$137.45	$137.45	$137.40
7 purchase totals =	$745.84		$814.7008	$814.70	$814.75	$814.60