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	$244.51	13.718%	$278.0519	$278.05	$278.05	$278.10
Purchase #2	$42.75	13.743%	$48.6251	$48.63	$48.65	$48.60
Purchase #3	$217.66	6.366%	$231.5162	$231.52	$231.50	$231.50
Purchase #4	$75.91	13.448%	$86.1184	$86.12	$86.10	$86.10
Purchase #5	$69.82	12.278%	$78.3925	$78.39	$78.40	$78.40
Purchase #6	$85.45	7.558%	$91.9083	$91.91	$91.90	$91.90
Purchase #7	$127.47	4.381%	$133.0545	$133.05	$133.05	$133.10
7 purchase totals =	$863.57		$947.6669	$947.67	$947.65	$947.70