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	$69.27	4.522%	$72.4024	$72.40	$72.40	$72.40
Purchase #2	$162.61	3.871%	$168.9046	$168.90	$168.90	$168.90
Purchase #3	$105.85	8.186%	$114.5149	$114.51	$114.50	$114.50
Purchase #4	$51.82	4.647%	$54.2281	$54.23	$54.25	$54.20
Purchase #5	$210.46	3.241%	$217.281	$217.28	$217.30	$217.30
Purchase #6	$176.97	8.832%	$192.6	$192.60	$192.60	$192.60
Purchase #7	$164.79	11.467%	$183.6865	$183.69	$183.70	$183.70
7 purchase totals =	$941.77		$1,003.6175	$1,003.61	$1,003.65	$1,003.60