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	$33.54	12.548%	$37.7486	$37.75	$37.75	$37.70
Purchase #2	$83.37	8.249%	$90.2472	$90.25	$90.25	$90.20
Purchase #3	$105.80	11.165%	$117.6126	$117.61	$117.60	$117.60
Purchase #4	$181.64	5.774%	$192.1279	$192.13	$192.15	$192.10
Purchase #5	$127.68	10.360%	$140.9076	$140.91	$140.90	$140.90
Purchase #6	$65.79	10.390%	$72.6256	$72.63	$72.65	$72.60
Purchase #7	$132.88	3.346%	$137.3262	$137.33	$137.35	$137.30
7 purchase totals =	$730.70		$788.5957	$788.61	$788.65	$788.40