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	$232.41	10.524%	$256.8688	$256.87	$256.85	$256.90
Purchase #2	$50.79	6.603%	$54.1437	$54.14	$54.15	$54.10
Purchase #3	$192.78	7.625%	$207.4795	$207.48	$207.50	$207.50
Purchase #4	$231.30	3.732%	$239.9321	$239.93	$239.95	$239.90
Purchase #5	$84.95	4.826%	$89.0497	$89.05	$89.05	$89.00
Purchase #6	$219.54	9.722%	$240.8837	$240.88	$240.90	$240.90
Purchase #7	$119.65	7.432%	$128.5424	$128.54	$128.55	$128.50
7 purchase totals =	$1,131.42		$1,216.8999	$1,216.89	$1,216.95	$1,216.80