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	$164.33	8.500%	$178.2981	$178.30	$178.30	$178.30
Purchase #2	$237.89	3.202%	$245.5072	$245.51	$245.50	$245.50
Purchase #3	$151.98	9.747%	$166.7935	$166.79	$166.80	$166.80
Purchase #4	$207.79	11.360%	$231.3949	$231.39	$231.40	$231.40
Purchase #5	$125.49	6.295%	$133.3896	$133.39	$133.40	$133.40
Purchase #6	$104.64	6.781%	$111.7356	$111.74	$111.75	$111.70
Purchase #7	$92.78	12.678%	$104.5426	$104.54	$104.55	$104.50
7 purchase totals =	$1,084.90		$1,171.6615	$1,171.66	$1,171.70	$1,171.60