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	$41.66	6.761%	$44.4766	$44.48	$44.50	$44.50
Purchase #2	$57.58	11.692%	$64.3123	$64.31	$64.30	$64.30
Purchase #3	$92.55	12.256%	$103.8929	$103.89	$103.90	$103.90
Purchase #4	$85.85	13.674%	$97.5891	$97.59	$97.60	$97.60
Purchase #5	$224.91	5.162%	$236.5199	$236.52	$236.50	$236.50
Purchase #6	$136.62	12.312%	$153.4407	$153.44	$153.45	$153.40
Purchase #7	$202.47	8.454%	$219.5868	$219.59	$219.60	$219.60
7 purchase totals =	$841.64		$919.8183	$919.82	$919.85	$919.80