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	$54.31	9.275%	$59.3473	$59.35	$59.35	$59.30
Purchase #2	$233.66	7.798%	$251.8808	$251.88	$251.90	$251.90
Purchase #3	$150.50	11.626%	$167.9971	$168.00	$168.00	$168.00
Purchase #4	$13.86	7.705%	$14.9279	$14.93	$14.95	$14.90
Purchase #5	$134.99	5.865%	$142.9072	$142.91	$142.90	$142.90
Purchase #6	$117.98	4.324%	$123.0815	$123.08	$123.10	$123.10
Purchase #7	$137.61	11.420%	$153.3251	$153.33	$153.35	$153.30
7 purchase totals =	$842.91		$913.4669	$913.48	$913.55	$913.40