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	$235.59	12.637%	$265.3615	$265.36	$265.35	$265.40
Purchase #2	$104.49	5.167%	$109.889	$109.89	$109.90	$109.90
Purchase #3	$221.33	10.589%	$244.7666	$244.77	$244.75	$244.80
Purchase #4	$156.92	12.458%	$176.4691	$176.47	$176.45	$176.50
Purchase #5	$133.43	4.874%	$139.9334	$139.93	$139.95	$139.90
Purchase #6	$133.72	11.121%	$148.591	$148.59	$148.60	$148.60
Purchase #7	$20.27	3.248%	$20.9284	$20.93	$20.95	$20.90
7 purchase totals =	$1,005.75		$1,105.9390	$1,105.94	$1,105.95	$1,106.00