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	$116.46	13.644%	$132.3498	$132.35	$132.35	$132.30
Purchase #2	$105.39	5.468%	$111.1527	$111.15	$111.15	$111.20
Purchase #3	$46.76	10.378%	$51.6128	$51.61	$51.60	$51.60
Purchase #4	$177.51	8.143%	$191.9646	$191.96	$191.95	$192.00
Purchase #5	$148.97	12.837%	$168.0933	$168.09	$168.10	$168.10
Purchase #6	$246.25	6.145%	$261.3821	$261.38	$261.40	$261.40
Purchase #7	$53.73	6.521%	$57.2337	$57.23	$57.25	$57.20
7 purchase totals =	$895.07		$973.7890	$973.77	$973.80	$973.80