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	$122.31	3.582%	$126.6911	$126.69	$126.70	$126.70
Purchase #2	$177.99	10.576%	$196.8142	$196.81	$196.80	$196.80
Purchase #3	$36.46	11.678%	$40.7178	$40.72	$40.70	$40.70
Purchase #4	$53.65	6.440%	$57.1051	$57.11	$57.10	$57.10
Purchase #5	$228.69	8.645%	$248.4603	$248.46	$248.45	$248.50
Purchase #6	$109.32	13.258%	$123.8136	$123.81	$123.80	$123.80
Purchase #7	$138.75	3.804%	$144.0281	$144.03	$144.05	$144.00
7 purchase totals =	$867.17		$937.6302	$937.63	$937.60	$937.60