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	$109.25	13.183%	$123.6524	$123.65	$123.65	$123.70
Purchase #2	$231.53	4.628%	$242.2452	$242.25	$242.25	$242.20
Purchase #3	$249.89	12.332%	$280.7064	$280.71	$280.70	$280.70
Purchase #4	$133.32	12.713%	$150.269	$150.27	$150.25	$150.30
Purchase #5	$141.66	9.617%	$155.2834	$155.28	$155.30	$155.30
Purchase #6	$110.54	3.700%	$114.63	$114.63	$114.65	$114.60
Purchase #7	$227.83	9.359%	$249.1526	$249.15	$249.15	$249.20
7 purchase totals =	$1,204.02		$1,315.9390	$1,315.94	$1,315.95	$1,316.00