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	$235.66	11.156%	$261.9502	$261.95	$261.95	$262.00
Purchase #2	$84.74	8.648%	$92.0683	$92.07	$92.05	$92.10
Purchase #3	$54.51	13.824%	$62.0455	$62.05	$62.05	$62.00
Purchase #4	$119.72	13.691%	$136.1109	$136.11	$136.10	$136.10
Purchase #5	$97.56	12.360%	$109.6184	$109.62	$109.60	$109.60
Purchase #6	$82.98	3.140%	$85.5856	$85.59	$85.60	$85.60
Purchase #7	$30.38	5.595%	$32.0798	$32.08	$32.10	$32.10
7 purchase totals =	$705.55		$779.4587	$779.47	$779.45	$779.50