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	$182.37	10.111%	$200.8094	$200.81	$200.80	$200.80
Purchase #2	$47.27	5.473%	$49.8571	$49.86	$49.85	$49.90
Purchase #3	$199.79	5.649%	$211.0761	$211.08	$211.10	$211.10
Purchase #4	$168.59	13.499%	$191.348	$191.35	$191.35	$191.30
Purchase #5	$173.33	10.650%	$191.7896	$191.79	$191.80	$191.80
Purchase #6	$151.34	3.566%	$156.7368	$156.74	$156.75	$156.70
Purchase #7	$74.59	13.423%	$84.6022	$84.60	$84.60	$84.60
7 purchase totals =	$997.28		$1,086.2192	$1,086.23	$1,086.25	$1,086.20