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	$39.52	10.139%	$43.5269	$43.53	$43.55	$43.50
Purchase #2	$73.25	7.144%	$78.483	$78.48	$78.50	$78.50
Purchase #3	$149.31	6.327%	$158.7568	$158.76	$158.75	$158.80
Purchase #4	$7.45	6.464%	$7.9316	$7.93	$7.95	$7.90
Purchase #5	$167.37	7.805%	$180.4332	$180.43	$180.45	$180.40
Purchase #6	$193.93	12.353%	$217.8862	$217.89	$217.90	$217.90
Purchase #7	$234.64	7.808%	$252.9607	$252.96	$252.95	$253.00
7 purchase totals =	$865.47		$939.9784	$939.98	$940.05	$940.00