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	$10.63	8.260%	$11.508	$11.51	$11.50	$11.50
Purchase #2	$38.42	13.127%	$43.4634	$43.46	$43.45	$43.50
Purchase #3	$85.31	10.307%	$94.1029	$94.10	$94.10	$94.10
Purchase #4	$95.98	8.421%	$104.0625	$104.06	$104.05	$104.10
Purchase #5	$210.95	5.858%	$223.3075	$223.31	$223.30	$223.30
Purchase #6	$20.83	5.425%	$21.96	$21.96	$21.95	$22.00
Purchase #7	$105.92	3.278%	$109.3921	$109.39	$109.40	$109.40
7 purchase totals =	$568.04		$607.7964	$607.79	$607.75	$607.90