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	$57.36	7.268%	$61.5289	$61.53	$61.55	$61.50
Purchase #2	$196.39	10.418%	$216.8499	$216.85	$216.85	$216.80
Purchase #3	$27.65	12.167%	$31.0142	$31.01	$31.00	$31.00
Purchase #4	$16.61	13.724%	$18.8896	$18.89	$18.90	$18.90
Purchase #5	$168.92	11.466%	$188.2884	$188.29	$188.30	$188.30
Purchase #6	$151.25	12.619%	$170.3362	$170.34	$170.35	$170.30
Purchase #7	$176.61	5.671%	$186.6256	$186.63	$186.65	$186.60
7 purchase totals =	$794.79		$873.5328	$873.54	$873.60	$873.40