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	$71.96	5.446%	$75.8789	$75.88	$75.90	$75.90
Purchase #2	$136.68	10.793%	$151.4319	$151.43	$151.45	$151.40
Purchase #3	$131.46	9.762%	$144.2931	$144.29	$144.30	$144.30
Purchase #4	$38.49	6.378%	$40.9449	$40.94	$40.95	$40.90
Purchase #5	$182.70	4.159%	$190.2985	$190.30	$190.30	$190.30
Purchase #6	$29.41	5.624%	$31.064	$31.06	$31.05	$31.10
Purchase #7	$117.88	5.406%	$124.2526	$124.25	$124.25	$124.30
7 purchase totals =	$708.58		$758.1639	$758.15	$758.20	$758.20