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	$112.81	12.632%	$127.0602	$127.06	$127.05	$127.10
Purchase #2	$224.66	11.247%	$249.9275	$249.93	$249.95	$249.90
Purchase #3	$217.57	4.539%	$227.4455	$227.45	$227.45	$227.40
Purchase #4	$184.72	3.719%	$191.5897	$191.59	$191.60	$191.60
Purchase #5	$86.76	3.607%	$89.8894	$89.89	$89.90	$89.90
Purchase #6	$174.49	4.106%	$181.6546	$181.65	$181.65	$181.70
Purchase #7	$200.67	4.143%	$208.9838	$208.98	$209.00	$209.00
7 purchase totals =	$1,201.68		$1,276.5507	$1,276.55	$1,276.60	$1,276.60