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	$28.88	10.180%	$31.82	$31.82	$31.80	$31.80
Purchase #2	$185.35	13.607%	$210.5706	$210.57	$210.55	$210.60
Purchase #3	$240.61	13.309%	$272.6328	$272.63	$272.65	$272.60
Purchase #4	$49.32	11.249%	$54.868	$54.87	$54.85	$54.90
Purchase #5	$174.69	8.687%	$189.8653	$189.87	$189.85	$189.90
Purchase #6	$107.87	10.176%	$118.8469	$118.85	$118.85	$118.80
Purchase #7	$166.97	6.544%	$177.8965	$177.90	$177.90	$177.90
7 purchase totals =	$953.69		$1,056.5001	$1,056.51	$1,056.45	$1,056.50