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	$189.91	8.612%	$206.265	$206.27	$206.25	$206.30
Purchase #2	$203.91	3.270%	$210.5779	$210.58	$210.60	$210.60
Purchase #3	$77.51	12.351%	$87.0833	$87.08	$87.10	$87.10
Purchase #4	$132.63	6.520%	$141.2775	$141.28	$141.30	$141.30
Purchase #5	$176.81	8.121%	$191.1687	$191.17	$191.15	$191.20
Purchase #6	$90.31	10.829%	$100.0897	$100.09	$100.10	$100.10
Purchase #7	$136.83	8.591%	$148.5851	$148.59	$148.60	$148.60
7 purchase totals =	$1,007.91		$1,085.0472	$1,085.06	$1,085.10	$1,085.20