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	$136.47	10.380%	$150.6356	$150.64	$150.65	$150.60
Purchase #2	$43.86	7.159%	$46.9999	$47.00	$47.00	$47.00
Purchase #3	$214.76	3.384%	$222.0275	$222.03	$222.05	$222.00
Purchase #4	$151.28	10.579%	$167.2839	$167.28	$167.30	$167.30
Purchase #5	$167.63	13.795%	$190.7546	$190.75	$190.75	$190.80
Purchase #6	$112.93	9.628%	$123.8029	$123.80	$123.80	$123.80
Purchase #7	$70.72	13.575%	$80.3202	$80.32	$80.30	$80.30
7 purchase totals =	$897.65		$981.8246	$981.82	$981.85	$981.80